President Reagan began dismantling the government's job development programs just when they were beginning to work, according to two new studies of Comprehensive Employment and Training Act (CETA) projects.

Both studies were financed by the Carter administration's Labor Department. Both come in the midst of the Reagan administration's efforts to revise the law, expiring next September, which established CETA.

The studies say that many problems affecting CETA operations have been eliminated since 1978, when the 1973 act was amended and extended for four years.

"Chronic problems that plagued CETA have largely been overcome by the amendments," according to one of the studies, conducted by the Washington-based Bureau of Social Science Research Inc. (BSSR) under a $500,000 government grant. That success came too late to stop the administration from wiping out the CETA public service employment project and from cutting CETA's total spending from $7.6 billion in fiscal 1981 to $4.5 billion projected for the current year, the report said.

Albert Angrisani, assistant labor secretary for employment and training, said yesterday he has seen neither the BSSR study nor the other report, a review of CETA job training programs by Public/Private Ventures (PPV), a Philadelphia-based research firm.

"There are many CETA reports" funded by previous administrations "that are coming in now," Angrisani said. He said his agency is trying to look at as many of the reports as possible but the administration most likely will use its own thinking in deciding CETA's future.

"We have our own ideas and, quite frankly, we're not going to play our hand until we see how things shape up," Angrisani said.

CETA programs have frequently been criticized for giving jobs to ineligible recipients--persons who were neither poor nor members of minority groups--and for allowing local governments to subsidize their payrolls with federal dollars.

By 1980, however, 93 percent of CETA enrollees were low-income people, compared with 74 percent in 1978, and the programs were reaching more people who were high school dropouts and chronically unemployed--"enrollees . . . more likely to be receiving public assistance," the BSSR study said.

The study also said that because CETA programs had been redirected to serve more poor and unskilled people, local officials were less inclined to use CETA money to subsidize jobs normally covered by the local payroll.

"The most significant change in the management of CETA between 1978 and 1980 was the tightening of program compliance at all levels of the administration," the BSSR report said.

The PPV study, in what it called "early and tentative" findings, said CETA's youth employment training programs were beginning to yield positive results. For example, the study said enrollees in the CETA-funded Jobs for Youth program in Boston, Chicago and New York earned an average of $22.08 more per week than their employed peers who had not been in the program.