Investigating the impact of exogenous input of nutrients on the stoichiometric ratio of carbon (C), nitrogen (N), and phosphorus (P) in arable soil is of significance for better understanding of the cycling and interaction of C and N in agroecosystems. Based on a 26-years fertilization experiment in a cropland, we analyzed content and stoichiometric ratio of C, N, and P in bulk soil, soil organic matter, and microbial biomass under various fertilization treatments. The regulation coefficient, H was calculated according to the model y=cx^1/H, where y is consumer stoichiometry, x is resource stoichiometry, c is a constant and H is regulation coefficient. Results showed that, compared with fallow (CK₀), soil microbial biomass nitrogen under the manure treatments (MNPK and 1.5MNPK) with cropping, significantly decreased, but soil microbial biomass phosphorus was significantly increased (P < 0.05). Long-term application of chemical fertilizers significantly decreased organic P. The C:N ratio in bulk soil, soil organic matter, and soil microbial biomass under treatments with organic amendments (maize straw and livestock manure) was significantly lower than that of the chemical fertilization treatments (N, NP, PK, and NPK). Compared with CK₀ treatment, application of P (chemical P fertilizer or organic amendments) significantly reduced C:P ratio in bulk soil and soil microbial biomass, but no fertilization (CK) and unbalanced fertilization treatments (N, NP, and PK) significantly decreased C:P ratio of soil organic matter. The N:P ratio under CK₀ treatment was the highest of all treatments. Moreover, N:P ratio of soil organic matter under CK₀ treatment was higher than that of the CK and the chemical fertilization treatments, indicating the N depletion in soil organic matter under CK and chemical fertilization treatments. The homeostatic regulation coefficient H of C:N, C:P, N:P was 0.24, 0.75, 0.64, respectively, indicating no stoichiometric homeostatic characteristic. There were significant positive correlations of C:N, C:P, and N:P ratios between bulk soil and soil microbial biomass. However, there was no significant relationship of C:N,C:P,and N:P ratios between soil organic matter and soil microbial biomass. Our results indicated that change in soil carbon, nitrogen, and phosphorus can directly affect the stoichiometric ratio in soil microbial biomass. The stoichiometric ratio of soil organic matter might be influenced by cropping and nutrients management practices, other than the stoichiometric ratio in soil microbial biomass.