In this paper, we describe the method of measuring the duration and the coherence time of ultrashort laser pulses using the technique of transient grating induced by laser. The two beams from the same laser interfer in the nonlinear medium and induce an integrated-intensity grating. Measureing the self-diffraction signal intensity versus the delay time between the two laser pulses and using the forth-order coherence function, we can get the duration of the laser pulse and coherence time.