This paper presented a flat belt transmission experimental system in order to investigate the nonlinear vibration during belt transmission. The servo controller drives a motor to produce the belt transmission, whose revolving speed is determined by output analog voltage of a multifunctional control card. A laser displacement sensor and LK Navigator software were used to measure the transverse vibration displacement. Experiments were conducted in some different speed conditions, including the uniform rotation and parametric excitation. The measured results from experiments verified the existence of nonlinear phenomena.