The noise enhancement effect of photovoltaic HgCdTe detectors caused by ultrashort pulse laser is discovered in experimental study, and its source and induction routes are researched through the experiments. The suggestions to suppress the noise enhancement effect are proposed. Experimental results show that the noise enhancement effect is primarily caused by the amplifying power supply of the ultrashort pulse laser at high-frequency which would produce stronger electromagnetic pulse. The electromagnetic pulse passes through free space to induce directly the circuits of detectors to produce noise enhancement effect, and the external link circuit between the detector and the laser and the photosensitive element is not the main association. Electrostatic shield and extending the distance between the detector and the laser can effectively reduce this kind of noise.