In this paper, a new non-uniform fault model with crooked fault surface is proposed. The crooked fault surface has been simplified as zigzag shape. When the slip and the travel velocity of dislocation on each saw tooth are uniforrm, we have found the analytic solution in enclosed form for the simplified problem. The amplitude spectra of body wave radiation have been calculated for different numbers of tooth, inclined angles of tooth and position angles of the field. The studied results show:1) the crooked fault can make unusual peak appear in spectral curve, the position of the peak is dependent on the tooth number, and moves towards the point of high frequency as the number increasing; 2) the change of the inclined angle can cause the change of spectral envelope line near the unusual peak; 3) the shape of amplitude spectrum is different for the observing point with different position angles. Comparing observed with theoretic spectra carefully, ones perhaps understand the non-planar feature of fault surface.