Conservative opponents to federal appeals court nominee Patricia M. Wald made her views on children's rights the major issue of a prolonged, four-hour confirmation hearing yesterday before the Senate Judiciary Committee.

Sen. Gordon J. Humphrey (R-N.H.) told the committee members that Wald, assistant attorney general for legislative affairs, favors "bizzare changes" in the family structure and has advocated "preposterous and proposals" in connection with the rights of children.

Dr. Bob Jones III, fundamentalist president of Bob Jones University in South Carolina, called Wald an "instrument of the devil" and urged the committee to reject her nomination to the U.S. Appeals Court here "in the interests of morality and decency in America."

Later in the hearing, committee member Sen. Strom Thurmond (R-S.C.), spent close to an hour questioning Wald about statements she had made on lowering the voting age, parental authority, children's rights to go to court, choose their schools and jobs and spend their own money.

Wald, 50, the mother of five children, assured Thurmond that she did not advocate lowering the voting age, that she thought children should have the right to legal representation in extreme situations - like committment to mental hospitals - and that "the law as a norm should keep hands off of the normal give-and-take in the home."

Wald was nominated by President Carter last March to fill one of two newly created seats on the court. A graduate of the Yale Law School, Wald worked briefly as an attorney with Arnold and Porter in Washington before taking 10 years off to raise her family.

She returned to legal practice in the erly 1960s with various public interest law groups, including neighborhood legal services and a mental health law practice before joining the Justice Department in 1977.

During the hearing yesterday, former D.C. Bar President Charles R. Work described the opposition to Wald as "preposterous and outrageous" and described the nominee as "an open-mined lawyer" with an "excellent temperament" who was a "calming and moderating influence" within the local bar.

Work, a Republican, accused the conservatives of taking Wald's comments about children's rights "out of context" from a 1974 article published in Human Rights magazine.

The views in that article, the focus of Humphrey's attack and Thurmond's questions, became the main issue at yesterday's hearing.

"I took the liberty of being provocative and now I'm paying the price for it," Wald commented during her questioning by Thurmond.

In an apparent effort to soften the conservative questioning that was to come, Sen. Birch Bayh opened the hearing by asking Wald to state her views on activist judges, the voting age and teen-agers' access to information on family planning.

Wald responded that she would leave "all appointed to the bench; that she did not advocate a change in the voting age but thought some children below the age of 18 are intelligent enough to vote, and said that information on nonprescriptive contraception should be available to adolescents "but in a context of counseling and planning."

The committee is scheduled to meet on June 26 to consider Wald's nomination, which must then be confirmed by the Senate. CAPTION: Picture, PATRICIA M. WALD . . . testifies before Senate panel