Abstract: The parameters affecting the period of a simple pendulum are studied. The conclusions are that the more the oscillation angle, the size of the oscillating ball, the latitude degree of earth, the height of the object above ground, the coefficient of viscosity of medium, and the density of medium, the more the period; the more the latitude degree of the earth, the less the period relavant curves are given.

Key words: simple pendulum, period, parameter, influence