Abstract: A 2year field experiment was conducted to study the effects of CaCN₂ combined with cucumber straw retention on soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN) and soil enzyme activities under cucumber continuous cropping system. Four treatments were used in this study as follows: CK (null CaCN₂), CaCN₂90 (1350 kg CaCN₂·hm^-2), CaCN₂60 (900 kg CaCN₂·hm^-2), CaCN₂30 (450 kg CaCN₂·hm^-2). The results indicated that, compared with the other treatments, CaCN₂90 treatment significantly decreased SMBC in 0-10 cm soil layer at seedling stage, but increased SMBC in 0-20 cm soil layer after earlyfruit stage. Compared with CK, CaCN₂ increased SMBC in 0-20 cm soil layer at latefruit stage, and increased SMBN in 0-10 cm soil layer at mid and latefruit stages, however there was no significant trend among CaCN₂ treatments in the first year (2012), while in the second year (2013) SMBN increased with the increasing CaCN₂ amount after midfruit stage. CaCN₂ increased straw decaying and nutrients releasing, and also increased soil organic matter. Furthermore, the CaCN₂90 could accelerate straw decomposition. Compared with CK, CaCN₂ effectively increased soil urease, catalase and polyphenol oxidase activity. The soil urease activity increased while the polyphenol oxidase activity decreased with the increase of CaCN₂, and CaCN₂60 could significantly improve catalase activity. Soil organic matter, urease activity and catalase activity had significant positive correlations with SMBC and SMBN. However, polyphenol oxidase activity was negatively correlated to SMBC and SMBN. Our findings indicated that CaCN₂ application at 900 kg·hm^-2 combined with cucumber straw retention could effectively improve soil environment, alleviating the soil obstacles under the cucumber continuous cropping system.