The invention discloses a four-bar mechanism teaching aid, and belongs to the technical field of machinery class teaching aids. The four-bar mechanism teaching aid comprises a spring, a transmission gear, a first connecting bar, a second connecting bar, a third connecting bar, a fourth connecting bar, a fifth connecting bar, a sixth connecting bar, a seventh connecting bar, an eighth connecting bar and a bottom plate. A gear shaft of the transmission gear is installed on the bottom plate in a rotation mode. The spring is meshed with the transmission gear. One end of the first connecting bar is fixed to the gear shaft. The first connecting bar, the second connecting bar and the third connecting bar form a double-crank mechanism. The first connecting bar, the third connecting bar and the fourth connecting bar form another double-crank mechanism. The fourth connecting bar, the fifth connecting bar and the sixth connecting bar form a crank rocker mechanism. The sixth connecting bar, the seventh connecting bar and the eighth connecting bar form a double-rocker mechanism. The four-bar mechanism teaching aid is convenient to carry and saves the time and labor.