The effect of different ambient temperatures on the electrochemical properties of La4MgNi17.5Co1.5 hydrogen storage alloy was investigated. The X-ray diffraction pattern shows that the alloy consists of LaNi5-type phase and A5B19-type (Ce5Co19 + Pr5Co19) phase. With the increase of the ambient temperature, the maximum discharge capacity of the alloy electrodes increases from 353.33 (283 K) to 379.25 mAh/g (308 K), and the cyclic stability (S100) of the electrodes decreases from 80.19 (283 K) to 52.04% (308 K) due to the acceleration of pulverization, corrosion and oxidation at higher ambient temperature. Moreover, it is found that the increase of the temperature can accelerate the diffusion rate of hydrogen in the alloy (D) and increase the exchange current density (I0), which are beneficial for improving the activation performance and the high-rate dischargeability (HRD) of the alloy electrodes. The activation cycles of the electrodes decrease from 4 (283 K) to 1 (308 K), and the HRD900 of the electrodes sharply increases from 66.36 (283 K) to 95.64% (308 K).