This study evaluated the effect of biochar on the soil nutrients, soil enzyme activity, and rice yield in a heavily saline-sodic paddy soil using a 2-year field experiment conducted in Jilin province in the northeastern part of China. The soil was amended with biochar at 0 biochar (B0), 33.75 t ha(-1) (B1), 67.5 t ha(-1) (B2), and 101.25 t ha(-1) (B3). The field experiment was arranged in a randomized complete block design. Each treatment was replicated three times. The results show that the addition of biochar significantly increased the availability of soil total N, available P, and available K, while it remarkably reduced the content of the soil's alkali-hydrolysable nitrogen, among which NH4-N and NO3-N were reduced significantly in 2 years. Biochar applications significantly increased the soil organic matter and soil C/N ratio. The soil Na+/K+ ratio was significantly reduced after biochar application in both 2 years. All of the biochar amendment applications improved the soil catalase activity, soil alkaline phosphatase activity, soil urease activity, and soil sucrose activity. The rice biomass, grain yield, and harvest index were significantly increased. Biochar applications can improve the soil nutrient status, decrease Na+/K+ concentration in soil, promote rice growth, and increase the rice yield in heavily saline-sodic paddy soils. It is anticipated that the study results will be useful for formulating novel management ways for improving crop production on saline-sodic soil.