Abstract In this paper, the hydrogen storage properties of (La–Ce–Ca)Ni 5 alloys were studied and an empirical equation was deduced for predicting the dependence of hydrogen dissociation pressure on the composition of the alloys. The theoretically predicted curves are in good agreement with the experimental results. Based on the theoretical analysis and experimental results, La 0.4 Ce 0.4 Ca 0.2 Ni 5 was selected as the hydrogen storage alloy for a metal hydrogen hydride compressor (MHHC). It absorbs hydrogen at 298 K and 1.9 MPa and desorbs hydrogen at 371 K and 12.0 MPa. Moreover, using industrial hydrogen with 98% purity. The MHHC produces ultrapure product hydrogen with 99.9999% purity. Namely, the compressor integrates the compression function with purification function.