By a relatively narrow 44-to-39 percent, a pluarity of the American people now favors the second Panama Canal treaty, scheduled for Senate vote during the last week of this month.

This treaty gives control of the canal to Panama after the year 2000, with the provisions that in an emergency, U.S. military forces will be allowed to defend the canal and U.S. warships will have priority in going through the canal. Without these provisions, Americans reject giving control of the canal to Panama by 60 to 29 percent.

The first of the two Panama Canal treaties was passed by the Senate last month by 68 to 32. This so-called neutrality treaty specifies that the canal will be neutral after the year 2000, allowing ships of all nations to pass through it. According to a recent Harris Survey of 1,199 adults nationwide, the Senate's vote is endorsed by the public by a 49 to 41 percent.

Although Americans now favor the two treaties by a narrow margin, they still are quite reluctant about handing over the canal. It was only the addition of the two key amendments dealing with the emergency rights for U.S. forces and warships - amendments supported by a 72-19 percent majority - that tipped the public in favor of the second treaty.

But even here there are sharp differences within the 44-to-39 percent plurality favoring the passage of the amended treaty:

By region, the Midwest gives the treaty the most support, with 46 to 37 percent in favor of it. But in the South, where resistance has been greatest from the beginning, a slim 42 to 41 percent pluarity still stands in opposition.

By age, people under 30 favor ratification of the second pact by a 55 to 34 percent, while those 50 years of age or over oppose its ratification by 42 to 33 percent.

By occupation, professional people favor the treaty by 55 to 32 percent, and white collar employes by 50 to 36 percent. But skilled labor is opposed by 43 to 42 percent and union members are evenly divided, 43 to 43 percent.

Sharp differences are also evident when the public's response is analyzed according to political philosophy and party membership. Conservatives oppose the second treaty by 43 to 38 percent, but liberals favor it by 57 to 29 percent. Democrats are for the treaty by 49 to 35 percent, Republicans oppose it by a razor-thin 41 to 40 percent, and independents split 42 to 42 percent.