Abstract: Three types of abnormal intensity noises of laser-diode(LD)-pumped Nd:YAG microchip laser were studied based on experimental data and theoretical analysis, including noises caused by the outside light feedback, the transmission of LD noise to solid laser and the mode coupling due to the deviation of end pumping. Corresponding methods were provided to eliminate these noises in order to suppress the intensity noise of the microchip Nd:YAG laser, improve the laser output characteristics and meet the demand of precision measurements.