In order to manufacture MOPA structure pulse single-frequency laser used for laser coherence imaging, the changes of temporal coherence of pulse single-frequency laser with the increment of laser power is required to be studied. This paper adopted acousto-optic Q-switch pulse single-frequency Nd:YVO4 laser as seed，and adopted Nd:YAG poweramplifier modules to double the power of seed laser. The Michelson interferometry was used to complete the measurement of the contrast of fringes of seed laser and amplifier under the optical path difference from 0 m to 6 m. Then, the change of temporal coherence of pulse single-frequency laser with the increment of laser power was primarily obtained. The measurements of basic parameters of seed laser and amplifier such as the property of single-frequency, pulse energy, pulse width and peak power etc was completed.