A new method of characterizing the femtosecond pulse is proposed based on the self-diffraction process in a thin transparent bulk medium and the self-reference spectral interferometry. A simple device is designed based on this technique and is successful in characterizing a ～40 fs pulse at 800 nm centeral wavelength. The result is in accordance with that measured by a commercial self-reference spectral phase interferometry for direct electric reconstruction. Pulses in a spectral range from deep UV to middle IR are expected to be measured by this new method and corresponding simple device.