The invention relates to a four-wave mixing scanning type ultrashort laser pulse time domain contrast measuring instrument, which comprises a beam splitter, a short-pass filter, a first planar reflecting mirror, a second planar reflecting mirror, a third planar reflecting mirror, a fourth planar reflecting mirror, an electric translation platform, a fifth plane reflecting mirror, a first cylindrical reflecting mirror, a second cylindrical reflecting mirror, a third-order nonlinear crystal, an attenuator, a filter, a detector and a computer, and is characterized in that laser light is decomposed into two beams of laser pulses with different frequencies through the beam splitter, the two beams of laser pulses with different frequencies shot to a third-order nonlinear material at a certain angle, two beams of four-wave mixing (Raman) signal light beams which are different from incident laser in frequency and different in propagation direction, and the intensity of generated signal light directly reflects the time domain contrast of the incident laser. According to the invention, four-wave mixing signal light which does not coincide with an incident beam in frequency is directly acquired, the device is simpler and high in stability, and the used components and nonlinear dielectric material are economic and cheap.