Prime Minister Abel Muzorewa, anticipating President Carter's decision not to lift sanctions against his government, said Carter was "frightened" about the effect a change in policy would have on his political career.

In an interview, Muzorewa predicted a de-escalation soon in the guerilla war wracking this country and said his personal envoys have been received sympathetically in at least nine black-ruled african countries recently.

Muzorewa's black-dominated government replaced the all-white one of former prime minister Ian Smith last week. It is now fighting for repeal of the economic sanctions imposed by the United Nations in 1966 after the Smith minority government declared the country independent of Britain's colonial rule.

Discussing the likelihood that President Carter would not unilaterally lift the sanctions, and thus give relief to Zimbabwe-Rhodesia's distressed economy, Muzorewa said, "We would feel terribly disappointed . . . to know that he would have taken this decision obviously not because he is trying to do something that is right but because he is just freightened by people who are perhaps threatening not to elect him." 'Sanctions Were Justified'

Muzorewa, whose English retains a tinge of an American accent acquired during the five years he studied in the United States, said that while Smith was in power, "those who stood on the side of supporting sanctions against his country were justified, and they had the right to do so because they were fighting a unilaterally established government here.

"But now, when the people of this country . . . voted their own government into power with 64.8 percent of the electorate voting, and then people continue to say nothing has happened, it hurts."

Muzorewa won Zimbabwe-Rhodesia's first multiracial national elections in April. The names of his Soviet-backed guerrilla opponents, Robert Mugabe and Joshua Nkomo, were not on the ballots. They refused to participate in an election held under the auspices of the Smith government.

"Having heard people talk about [Carter] as a committed Christian and having heard him talk in his election campaign about human rights, I would be disappointed in that . . . here is a country that is really suffering . . . because of sanctions."

The prime minister, who is under fire from many leaders of other black governments, as well as his two guerrilla opponents, for accepting a constitution that guarantees the white minority a political role far out of proportion to its numbers said today that his personal representatives have been "very well received" in at least nine blak-ruled African countries since he won the April elections.

"In fact we are very pleased to know they were not just received by ordinary small boys down there, but by people of real considerable position in those governments, like vice presidents, deputy prime ministers," Muzorewa said. 'Embarrassing Position'

He declined to name the states saying they had "not picked up courage" to openly support him and he would not like "to put them in that embarrassing position where I say these people support me." Muzorewa said, however, that they were all sympathetic to what his envoys had to say.

Muzorewa expressed confidence that increasing numbers of an estimated 12,000 guerrillas now inside the country would take advantage of the government's amnesty offer because "the situation is different."

"Although there are a lot of boys in the bush, they have been amazingly inactive, in other words quiet, and the main reason being that they themselves are inquiring how they can come home without getting into clashes with the security forces, he added.

"What is more . . . they have been rubbed with this communist idea of "respect of the masses' and they have seen the masses during the election going around to vote and no one can doubt in their minds . . . they know that the person who is there was elected by the people."