The average Chinese city dweller can expect a 25 percent increase in real income, a new social security system and, for the first time, regular annual vacations, if China's new five-year economic plan is realized, according to the official Chinese news agency.

The aim of the plan is to allow many Chinese to move from merely adequate living conditions to those that would provide a degree of comfort.

A Chinese official briefing reporters on a draft proposal of the plan said that China would continue its policy of opening to the outside world. The plan, which begins in 1986, would boost foreign trade by 50 percent and reduce state control of industry, he said.

A draft proposal of the plan was presented this week to delegates attending a special six-day Communist Party conference.

In a report on the draft proposal, the official New China News Agency said that under the new plan, the gap between urban and rural residents will be narrowed. Under the economic reforms that have been introduced here by China's top leader, Deng Xiaoping, and his senior colleagues, people living in the rural areas so far have benefited more than their urban counterparts. The government introduced urban economic reforms this year, while reforms in the countryside were introduced five years ago.

In a briefing for reporters at the Great Hall of the People, where the Communist Party conference is being held, Yuan Mu, deputy secretary general of a party economic and financial group, said that the consumption level of urban and rural residents should increase by about 25 percent.

Yuan said China already had solved the problem of providing adequate food and clothing for most of its people in the previous five-year plan. Now, he said, greater emphasis would be placed on improving housing conditions.

Yuan said the plan calls for doubling national output between 1980 and 1990, in keeping with Deng's aim of quadrupling growth by the year 2000 to approach the level of advanced countries.

The official Chinese news agency also said that output of consumer goods would rise and that a system of vacations should be instituted gradually for workers and government employes, based on improved labor efficiency. Without giving details, the news agency also said it was necessary to consider and establish a new social security system.