Prime Minister John Vorster appointed Information Minister Connie Mulder yesterday to administer matters relating to South Africa's 18 million blacks in a Cabinet reshuffle suggesting no substantial change in his racial policies.

Mulder is regarded as a conservative and strong supporter of Vorster's apartheid policy under which the black majority is subjected to separate development and discrimination.

Mulder, who is the prime contender to succeed Vorster, retained his information post and thus appeared to have strengthened his position in the Cabinet.

Another controversial figure, Minister of Justice Jimmy Kruger, retained his post despite widespread criticism in connection with the death in jail last September of Steve Biko, black consciousness leader.

But Vorster announced that the Ministry of Bantu Administration, Development and Education is to be split and that the word Bantu - the reference to blacks which they regard as denigrating - would be dropped.

Supervision of black education and training will become a new, separate ministry and will be headed by a moderate, William Cruywagen. His deputy, however, will be Andreis Treurnicht, who is regarded as spokesman for arch-conservative forces within Vorster's party.

There was hope among liberals here that Vorster might use the retirement of the Bantu affairs minister, M.P. Botha, to put a liberal into the position. The name frequently mentioned was that of Peter Koornhorf, the minister of national (white) education and sports.

Moderates here had also hoped that Foreign Minister Pik Botha, who along with some senior diplomats is said to favor a more conciliatory line in press relations, would take over the information protfolio, which Mulder has turned into a forum for hardline statements and anti-foreign diatribes. Botha was renamed foreign minister.

These expectations failed to materialize when Vorster announced his new Cabinet on the eve of a new parliamentary session, which opens tomorrow.

Overall, the changes have been minimal and they do not represent an ideological shift in Vorster's National Party after its landslide in the Nov. 30 elections.

The upgrading of the black education department clearly came in response to unrest among urban blacks during the past 20 months. Educational grievances have been the focus of their protests.

But Vorster's move fell short of black demands that their education be placed under the Ministry of National (white) Education.

The government's immediate task is to try to persuade black children to return to their classrooms in segregated townships. More than 300,000 black students boycotted classes last year, many staying away for months.

The Ministry of Interior, formerly held by Mulder, was given to Alwyn Schlebusch, who retained the immigration and public works protfolios. He is a conservative who led a 1973 crackdown on church and student groups opposed to apartheid.

Among the 19 Cabinet positions, only one went to a member of the English-speaking community. It was the Ministry of Finance, which is led by D.P.F. Horwood.

Helen Suzman, spokeswoman for the opposition Progressive Federal Party, criticized the reappointment of Kruger who she said displayed "incredible insensitivity" in the Biko case.

She also referred to the dropping of the term Bantu by saying: "What obviously is needed is more basic, more fundamental changes in policies. No one will be deceived by the fact that just the name was changed."