Transverse vibration of the serpentine belt is effective at noise and durability of it. Therefore, understanding of this phenomenon and studying effective parameters can be used in the process of reducing belt noise and increasing life time. In this paper, transverse vibration of serpentine belt is measured experimentally and analyzed. In the implementation test steps, the displacement of the belt in two positions has been measured. Then, the time signals were transformed to frequency domain. It is derived and observed that the belt vibration is synchronous with engine speed, accordingly order analysis is selected to analysis the vibration signal. Results show that the natural frequency of serpentine belt in the region between A/C compressor and crankshaft pulley changes due to A/C compressor loading, but this parameter is not affected by engine load variations. In the area between automatic tensioner and idler, natural frequency is constant regardless of A/C compressor on-off condition and engine load changing. In all engine rotating speeds, the dominant frequencies are highly closed to the natural frequencies. In some engine speeds, vibration amplitude is high and the frequency of these points are proportionally equal to 2, 3, 4 and other orders of engine speed.