Abstract: 22MnB5 steel for construction machinery was autenitizied first and then was subjected to direct quenching, quenching to different partitioning temperatures (305, 330 ℃), holding for different times (10, 20, 30, 60, 80, 100, 120 s) partitioning and quenching (one-step queching-partitioning) and quenching to 330 ℃ than partitioning at 405 ℃ for 20 s and quenching (two-step quenching-partitioning), respectively. The effect of quenching-partitioning process on the structure and properties of the test steel was studied. The results show that the one-step quenching-partitioning sample was mainly composed of martensite and carbides, and the quantity of carbides were relatively large and size were relatively small when the partitioning time was 60 s. The two-step quenching-partitioning sample was mainly composed of lath martensite, carbides and a small amount of massive martensite, and the decomposition of residual austenite was complete and the size of carbide was large. The direct quenching sample was composed of hardened lath martensite and a small amount of carbides. With the extension of the partitioning time, the tensile strength of one-step quenching-partitioning sample decreased, the percentage elongation after fracture increased first and then decreased and the product of strength and elongation decreased first and then increased and then decreased. The percentage elongation after fracture and product of strength and elongation reached the maximun values when the partitioning time was 60 s. The product of strength and elongation of the direct quenching sample, the two-step quenching-partitioning sample and the one-step quenching-partitioning sample increased successively.