The Chinese government yesterday denounced as "completely unacceptable" Senate action tightening safeguards on the new U.S.-China nuclear trade agreement that took effect yesterday.

The pact will guide the U.S. nuclear industry in bidding for contracts from China's proposed $6 billion nuclear-power construction program.

However, Foreign Ministry spokesman Li Zhaoxing said in Peking that a modification by Sen. John Glenn (D-Ohio) "raised unreasonable demands for the U.S. side to unilaterally change some substantive provisions" of the pact.

"Any unilaterally imposed additional provisions beyond the agreement are completely unacceptable," Li said.

The change would require the president to certify that nuclear materials sold to and bought from China are subject to International Atomic Energy Agency safeguards against the spread of nuclear weapons.

The change was attached to the catchall $498 billion government spending bill Monday, and the Reagan administration said Tuesday that the language would "undermine" the trade agreement and damage U.S. relations with China.

Officials promised to work to remove it from the final spending bill, still under debate in the House.

The House also approved, 307 to 112, a separate and milder resolution that in essence expressed concern about the lack of written assurance from the Chinese on their commitment to nonproliferation.

"The resolution does not go as far as many of us thought was necessary, but it is all we have," said Rep. Howard E. Wolpe (D-Mich.), a leading critic. He and Rep. Edward F. Feighan (D-Ohio) circulated a letter yesterday urging support for the Glenn amendment when it comes to the House-Senate conference committee.

Rep. Edward J. Markey (D-Mass.) told the House there is "monumental hypocrisy" in administration demands for elaborate on-site inspection of any peace agreement involving "tiny, bankrupt Nicaragua" when no such demands are made of China in this accord.

Rep. Gerald B. Solomon (R-N.Y.) said he voted against the resolution because it is "an open-ended formula for disaster."

To say that he disagreed with its substance "would assume that this agreement has substantive content, which it does not," Solomon said.