La1.3− x Sm x CaMg0.7Ni9 (x =0–0.3) hydrogen storage alloys were prepared by inductive melting and the effect of the Sm content on the structure and electrochemical properties was investigated in the paper. The Sm substitution for La in La1.3− x Sm x CaMg0.7Ni9 (x =0–0.3) alloys does not change the main phase structure (the rhombohedral PuNi3-type structure), but leads to a shrinkage of unit cell and a decrease of hydrogen storage capacity. With the increase of the Sm content in the alloys, the maximum discharge capacity of electrode decreases from 400.2 (x =0) to 346.6mAhg−1 (x =0.3), but the high-rate dischargeability and cycling stability is improved. After 100 cycles, the capacity retention rate increases from 75 (x =0) to 85% (x =0.3).