Law, a former president of Tallahassee Community College, has led the St. Petersburg school since 2010.
"I only have good feelings for the work we've accomplished," Law said in letter to the college's board of trustees. "For all of us there's a time to move on."
Law said he would help "facilitate the process of finding the next president" for the college, which serves more than 52,000 full- and part-time students on 10 campuses in Pinellas County.
Law is a former staff director of the Florida House Committee on Higher Education and a former president of Lincoln Land Community College in Springfield, Ill., and the founding president of Montgomery College near Houston.
While at St. Petersburg College, Law established The College Experience program, which was recognized for improving student success rates, particularly among first-time-in-college minority males.