When commencement exercises begin tomorrow at Dansallan College on the island of Mindanao in the Philippines, the school's missionary-president expects to preside over the ceremonies as scheduled.

The Rev. Loyd Van Vactor, 55, plans to hand out diplomas to his overwhelmingly Moslem student body despite the turmoil and tragedy that has racked his life over the past three weeks.

Three days ago Van Vactor unexpectedly returned to his home in Marawi City, about 50 miles south of Manila, after 17 days as a hostage of Moslem separatist guerrillas. It was up to his son, Norman, 22, to tell his father that five days earlier he and his brother, Ross, 17, had buried their mother who had died following emergency surgery for an intestinal obstruction.

Van Vactor and his wife, Masie, had served together for 27 years under the oldest foreign mission board in American Protestantism-the Board for World Ministries of the United Church of Chirst. Death in the line of duty is a commonplace throughout the annals of the board's 170-year history but the taking of missionaries as hostages in political disputes is a relatively new peril.With missionaries active in many politically tense areas of the third world, the Van Vactor kidnaping was watched with particular anxiety by church leaders.

Concerned with the possibility of setting a precedent, leaders of the United Church of Christ in the Philippines-to which Van Vactor was seconded by the American church-refused to pay the $67,000 ransom demanded by the knidnapers. After 17 harrowing days of death threats and ransom deadlines, which were extended several times by the kidnapers, Van Vactor was released.

"The Libyan ambassador [to the Philippines] played a very important part in the final negotiations," explained the Rev. Dr. David Stowe, New York, who heads the mission board. Stowe linked ambassador Mustaphi Dreiza's effectiveness to Libyan encouragement of the Moro National Liberation Front, which has waged a six-year campaign for Moslem independence in the Southern Philippines.

Dansallan College has existed for more than a half-century in Marawi City, one of the centers of the Moslem independence movement. Stowe however, credited involvement by the local Moslem community as "the key to the success of the negotiations" to free Van Vactor. Several Moslem civic leaders, including the mayor, made up the team that carried the burden of the negotiations.

Dansallan College was founded by the famed literacy pioneer. Frank Laubach. It was there that he developed his widely copied "each-one-teach-one" technique of education. "The college is what I would call a textbook model of a competently run mission program," Stowe said, "involving services, fellowship and Christian preaching."

Stowe said there were "very, very few, if any, conversions" from the Moslem faith to Christianity. The mission program seeks to evangelize, he said, "if you understand evangelism as telling the story of the Christian faith primarily through dees, through their [the missionaries'] lives."

Stowe as wella s sources in the Philippines attributed Van Vactor's kidnaping to a fringe guerrilla group. "We got a letter (from Van Vactor) the day after he was kidnaped-obviously written about a week earlier-saying that a group of guerrillas had entered the area and that everyone had been advised to take special precautions."

Stowe said Van Vactor's son, Norman, a senior at St. Olaf College, Northfield, Minn., flew home when his father was kidnaped and was with his mother when she died in a Manila hospital while the younger boy remained in Marawi "to help with the negotiations" for his father's release.