La0.3Y0.7Ni3.4-xMnxAl0.1(x=0-0.5) hydrogen storage alloys were prepared by vacuum arc melting fol¬lowed by homogenized annealing. Effect of Mn element on the microstructure, hydrogen storage behavior and elec¬trochemical properties were systematically investigated via different methods. The results show that the microstructure of the annealed alloys closely relates to the Mn content. Higher Mn content facilitates the formation of Ce2Ni7 type phase until single phase structure of Ce2Ni7- type forms in the alloys with x≥0.3. With the increment of Mn content, the unit cell parameters (a, c) and unit cell volume (V) of Ce2Ni7- type phase increase, resulting in the hydrogen absorption platform pressure of the alloys decreasing from 0.079 MPa to 0.017 MPa and the hydrogen storage capacities reaching 1.268wt%-1.367wt%. The electrochemical properties are significantly improved with the addition of Mn. La0.3Y0.7Ni3.25Mn0.15Al0.1 alloy exhibits the highest discharge capacity (390.4 mAh•g-1). The capacity retention S100 of the alloys with x=0.15 and 0.5 are 86.03% and 88.01%, respectively, presenting good cycle stability. Meanwhile, high rate discharge ability (HRD900) of the as-prepared alloys is 71.53%-87.73%. It is shown that electrochemical reaction kinetics of the alloy electrodes is controlled by both the electron transfer at the electrode/ solution interface and the diffusion of hydrogen atoms in the alloy bulk. © 2020, Science Press. All right reserved.