The Newtonian gravitational constant G，as the basic physical constant describing the strength of gravitational interaction between objects，was one of the earliest fundamental constants introduced by physicists．Due to the weakness and unshielablity fo gravity，G still remains the least precisely known among all fundamental physical constants yet．As one of the important experiments in the field of precision measurement physics，the G measurement experiment puts high demands on the accuracy of the measurement．Based on the principles of the time-of-swing method，a simple G measurement is designed，the pendulum，the source mass and their relative positions are accurately measured． Based on the designed device，the measurement result of the gravitational constant G is given by accumulating periodic data with or without the source mass． As an innovative experiment on physics teaching for undergraduates，it involves mechanics，kinematics，optics， metrology and other related college physics courses in the teaching and experiment process，which helps to cultivate students’logical thinking ability，practical ability，and scientific analysis ability，and deepen the understanding of relevant knowledge points and apply them．