Abstract: The aim of this study is to explore the changes and coupling characteristics of carbon (C), phosphorus (P) and microbial C, P in a hillslope cropland of purple soil. The results showed that total organic carbon (TOC) ranged from 90.8 to 100.8 g·kg^-1 under organic fertilizer or straw combined with inorganic fertilizer treatments (including N, NP and NPK) as compared with nitrogen (N) application only (62.2 g·kg^-1). Total phosphorus (TP) ranged from 0.65 to 0.84 g·kg^-1 in organic combined with inorganic fertilization treatments, and that under straw combined with inorganic fertilizer treatments was 23%-38% of organic fertilizer combined with inorganic fertilization treatments. The microbial biomass phosphorus (MBP) under N fertilizer was significantly decreased as compared with combined fertilization treatments. The ratios of microbial biomass carbon (MBC) to MBP under combined fertilization treatments were between 5 to 26, and the TOC/TP ratios under organic fertilizer and straw combined treatments were between 92 to 137 and 296 to 653, respectively, while those under N fertilizer treatment were 59 and 2000, respectively. The results indicated that combined organic and inorganic fertilizers would be helpful for enhancing P availability and increasing its potential capacity in purple soil.