Despite white fears of radical socialist changes under a black-ruled Zimbabwe, Prime Minister Robert Mugabe's first 100 days have left the white-dominated economic structure paractically intact.

In fact, the new government's first "people's budget" announced recently was so conservative that black Finance Minister Enos Nkala was jokingly branded a "capitalist" by a white member of Parliament.

According to visiting American political science professor Donald Baker, Mugabe, a self-avowed Marxist, has made fewer changes than Franklin D. Roosevelt did in his first 100 days in office in 1932.

Although a number of high-profile changes have been introduced to benefit the black majority, Mugabe has taken special care to avoid alienating the white minority that formerly ran the country.

Among the reasons for Mugabe's apparent concern about white sentiments is that he is dependent on the minority in several ways. It still controls the economy that provides jobs and can help alleviate critical unemployment among blacks with enough pratical experience to completely take over running the civil service, although plenty of blacks have adequate education.

The Mugabe government's conservatism also apparently reflects a desire to reassure the conservative tribal chieftains who often sided with the white government during its war against black nationalist guerrilas. The chieftains continue to wield great influence in the countryside.

In other parts of Africa, tribal chiefs have been shunned by Marxist-oriented politicians. Last weekend, however, Mugabe flew to the southwestern part of the country and met with more than 200 assembled chiefs and elders at one of their historic meeting grounds. He assured them that the government did not intend to abolish the institution of chieftainship and asked them to aid the government in carrying out its programs. They agreed.

Although Mugabe and his ministers have taken every occasion to remind their audiences, black or white, that more far-reaching changes are going to come, his administration's first 100 days suggest that these changes will be gradual and orderly.

Much like his predecessor, Bishop Abel Muzorewa, who was defeated in last February's British-supervised elections, Mugabe must balance black expectations of change with white fears of victimization and the loss of their privileged postion.

Unlike Muzorewa, however, Mugabe and his team have more than token power and are able to make meaningful chages. In addition, they are more politically attuned to the dangers of ignoring black aspirations.

To please its black electorate, Mugabe's government has reduced or eliminated the sales tax on a number of essential goods, promised free primary school educatin and medical services later this year and announced compensation for handicapped guerrillas or families of dead guerrillas who fought in the black nationalist war against the wite minority.

The government has also declared a minimum wage for all workers that ranges from $45 a month for house servants and farmhands to $105 a month for factory workers. Wage discrimination based on race and sex has been outlawed.

In addition, the government has encouraged the establishment of "workers' committees" in factories and farms to facilitate communication between employers and emplyes. High priority has been given to the resettlement of 660,000 people in the rural homes from which they were displaced by the war.

For whites, the most significant ecouragement has been the new budget.

It did not attempt to redistribute wealth by increasing taxes on higher incomes as many whites had expected, and it created a favorable climate for business and foreign investment by continuing the former government's policy of allowing new foreign capital investment to be repatriated after two years. The government also pledged not to interfere with pensions.

"The budget did go a long way to settling people," said Zimbabwean businessman who had said previously he ws skittish about the socialist direction of Mugabe's policies.

Whites have also been encourged by the fact that private and "community schools," which were introduced last year to prevent an influx of black students into previously all-white institutions, will be allowed continue and that the government will give them financial assistance.

In the sensitive area of "Africanizing" the civil serivce, Minister of Public Serivce Richard Hove has announced plans to leapfrog blacks over whites. But he said some of the bypassed whites would receive monetary compensation for their losses and that the process would be temporary until a more favorable racial balance was achieved in the civil service.

Last week, Mugabe and four of his ministers held a confidence-building session with a union of white farmers in Salisbury. They assured the farmers that reforms in land distribution and wages should not threaten the farmers' viability, productivity or security.

The farmers were asked to cooperate with the government in helping advance black peasant farmers. Already the government has announced drought relief and has guaranteed prices for next year's corn crop to encourage farmers to stay.