A California scientist has accused the Environmental Protection Agency of misrepresenting, changing and falsifying his research about a controversial poison that environmentalists oppose but cattlemen and sheep growers want legalized.

Dr. Ernest Kun, a professor at the University of California in San Francisco, claims testimony he gave last July before an EPA panel has been misused by Administrator Anne M. Gorsuch to justify re-examining the government's current ban on Compound 1080, a deadly poison once widely used in western states to kill coyotes and other predators.

"EPA obviously had a conclusion that it wanted to reach so it took his statement out of context, misconstrued it and made it just plain wrong to get the results it wanted," Joseph L. Cowan, a spokesman for Kun and the university, said yesterday.

William Wells, the EPA official who oversaw the drafting of the agency's response to Kun, said EPA has "studied Kun's accusations" but has decided to "stick with its own interpretation" of what the pharmacologist's research means when it conducts formal hearings later this month on the 1080 ban.

"We feel we have made an accurate representation of what he said in his testimony," said Wells. "He seems to be telling us things now that he didn't say in July."

EPA banned Compound 1080 in 1972, saying its use by ranchers and the government not only killed coyotes, but thousands of other animals and birds that fed on either 1080-treated bait or on animals which had eaten the bait and died.

Last year, western livestock owners asked Gorsuch to reconsider the ban because, they said, it had cost them millions of dollars in livestock losses to predators.

In December, Gorsuch said EPA had obtained "new information" which justified re-examining the ban. Gorsuch said the research showed that the carcasses of coyotes killed by 1080 were not themselves poisonous, that is, they did not contain enough 1080 to kill animals which then fed on them. EPA officials said later that Gorsuch was referring primarily to Kun's research on the "second kill" effect of 1080.

Kun called Gorsuch's statement false and misleading, and accused EPA of doctoring his testimony by substituting the word "non-toxic" for "biochemically unstable" when it quoted his findings. "There is a vast difference between a research finding of non-toxicity, as claimed by EPA, and one of instability," he said.

"We agree that the discussion of his conclusion in the press release Gorsuch's statement may be worded somewhat imprecisely," said Wells, but he said EPA did not "believe the statement was misleading to the public" because it conveyed "Dr. Kun's general hypothesis."

Kun also claimed EPA took two parts of his testimony "completely out of context" to make it appear as if it disagreed with testimony by another scientist, when it actually agreed with it. "EPA needed some pivotal scientific basis to justify and trigger these hearings," said Cowan, "so they . . . misrepresented his statements to justify the hearings."

Last month, President Reagan lifted the Nixon-imposed presidential ban which prohibited 1080 on federal lands. Environmentalists claimed his action was intended to press EPA into also lifting its ban.