The reliability analysis of Nd:YAG side-pumped laser based on GO (Goal Oriented) method is studied. The GO diagram model of the Nd:YAG side-pumped laser is established. The weak links of the Nd:YAG side-pumped laser are analyzed qualitatively, and the reliability results of each weak link in the laser head are calculated quantitatively, including the equivalent failure rate λ_R, equivalent maintenance rate μ_R, average fault-free operating time MTBF, etc. The effect of improving the failure rate of KTP crystal on the reliability of Nd:YAG side-pumped laser is quantitatively calculated. The GO diagram model established in this paper can provide a theoretical basis for the optimization and reliability evaluation of Nd:YAG side-pumped laser.