Samuel Cornelius is about to be a man out of work, and he is thrilled.

Cornelius, deputy director of the Community Services Administration, was sipping a drink at a reception for the opening of the third annual National Conference of Blacks in Government at the Washington Hilton.

"Come Sept. 30th we're not just gonna be cut back, we're gonna be cut out," said Cornelius. "I was in on the attempt to cut out CSA 10 years ago. I think the states ought to be coming up with the solutions to poverty. I reject the notion that people in Washington are the only ones with any brains." After Cornelius finished praising the number of black Reagan appointees, Jim Smith, chief of NASA's information resources management office, stepped in.

"That's ridiculous," said Smith. "The president is basically antiblack, antiminority and antiwomen. There are just too few black appointees in his administration. And he is watering down affirmative action."

For the next two days more than 6,000 delegates from various government agencies will participate in conferences on issues such as unemployment, civil rights and sexual discrimination. They also will hear speeches from key black government figures such as Atlanta Mayor Maynard Jackson.

The temperature in the Hilton's ninth-floor conference room was hot but the atmosphere congenial despite disagreements over administration policies.

St. George IbCrosse, a Baltimore minister and former Reagan campaign coordinator, said, "As a black Republican I feel a little like people did with the coming of the Roosevelt era. There is change happening, there is uncertainty. But, especially among professional blacks, I see a lot of switching to the Republican side. Blacks, even now, and even though they are usually represented by Democrats, are largely fiscal conservatives and conservatives on moral issues like abortion and busing."

Three feet away, Barbara Hutchinson, women's director of the American Federation of Government Employees, disagreed. "The consensus is that Reagan's policies, his budget cuts, his tax cuts, are leaving the all the burden on blacks, minorities of all kinds and especially government employes. Those are the people feeling the brunt of all this. It's not that blacks are getting more conservative, but they are more aware of the conservatives in their midst," she said.

Melvin Bradley, senior policy adviser to the president, said he finds great support among blacks for the administration.

"From the civil rights movement it was always perceived that the liberals were the good guys and the conservatives were the bad guys," said Bradley. "But blacks are more conservative than you might think. I think eventually the direction of black leadership will change."