In this study, three management practices, including clean tillage, natural grass mulching, and cultivated grass mulching, were identified as the research objects. The effects of long-term living grass mulching on the carbon (C), nitrogen (N), and phosphorus (P) contents of soil and microbial biomass and the soil enzyme activities in different soil layers in a citrus orchard as well as the correlations of these indicators were investigated by measuring the chemical and biological properties of soil. The results showed that grass types and soil layers had significant effects on the C, N and P contents of soil and microbial biomass and the corresponding enzyme activities. However, their interactions only showed significant effects on β-glucosidase, N-acetylglucosaminidase and leucine aminopeptidase (P<0.05). In general, the biochemical properties of soil were ranked in descending order in terms of grass types and soil layers:cultivated grass mulching > natural grass mulching > clean tillage among different grass types, and 0-10 cm > 10-20 cm > 20-40 cm among soil layers. The redundancy analysis results showed that the chemical and biological indices of soil in the first two axes accounted for 80.2% of the changes in soil enzyme activities and mainly showed positive effects. The effects of the chemical and biological indices of soil on enzyme activities varied with grass types and soil layers. The cultivated grass mulching showed positive effects on the activities of β-glucosidase, cellobiohydrolase, phenol oxidase, N-acetylglucosaminidase, leucine aminopeptidase and acid phosphatase in each soil layer. The natural grass mulching only had positive effects on β-glucosidase and cellobiohydrolase activities in the 0-20 cm soil layer. Soil enzyme activities of these two grass types were most significantly affected by the C, N and P contents of soil in the 0-10 cm soil layer. Therefore, compared with clean tillage, the cultivated and natural grass mulching significantly increased the C, N and P contents of soil and microbial biomass and the corresponding enzyme activities. However, their promotion effects on the C, N and P decreased with the increase in the soil depth. Particularly, the promotion effect of the cultivated grass on the C, N and P was larger than that of natural grass.