Pulse broadening has a great influence on the increase of inter symbol interference of wireless optical communication system. Based on the generalized Huygens-Fresnel principle and the modified von Karman spectrum model, a detailed numerical analysis on pulse broadening of the partially coherent Gaussian Schell model pulse (GSMP) beam propagation in atmospheric turbulence is discussed. The analytic expressions of the mean intensity and the pulse broadening of the partially coherent GSMP beam propagating in atmospheric turbulence in frequency domain and time domain are derived. The results indicate that the partially coherent GSMP beam is less affected by turbulence than the fully coherent GSMP beam, and that the smaller the partially coherent beam waist radius is, the more serious the beam is affected by turbulence. In the frequency domain, under the same propagation condition, the stronger the turbulence and the bigger the outer scale is, the more obvious the GSMP beams broadening effect is. In the time domain, with the increase of the initial pulse width, the relative pulse width at the receiver ending decreases rapidly. Within 40 femtoseconds, the relative pulse width is very obvious. With more than 40 femtoseconds, there is no significant difference between the pulse width on the receiver and the initial pulse width.