The rack and pinion mechanism of the rack and pinion pumping unit can produce fatigue damage due to longterm cyclic alternating load. Aiming at the fatigue life of the rack and pinion mechanism, the nominal stress method and the Miner linear damage theory were used to analyze the fatigue life of gears.An accurate rack and pinion mechanism model was drawn, and the transient dynamic analysis was carried out; by calculating the fatigue life of the mechanism, the stress cloud diagram, damage cloud diagram and fatigue life cloud diagram of the gear and rack were obtained. The results show that the stresses of the pinion and rack are mainly concentrated at the meshing part; the higher the roughness of the gear is, the lower the fatigue life is; the ambient temperature has little effect on the fatigue life of the gears. The research results provide reference for the structure optimization of rack and pinion pumping unit.