Forms of P and P sorption parameters in soils under different crop rotation systems in a 26a long-term fertilization field experiment in an arid loess plateau were determined for study of effects of crop rotation and fertilization on forms and adsorption of the phosphorus in the soil and relationships between soil phosphorus adsorption parameters and phosphorus forms. Results show that both long-term crop rotation and long-term fertilization reduced the maximum P adsorption capacity(Qm) of the soil; relative to other crop rotation and continuous cropping systems, the application of nitrogen and phosphorus fertilizer (NP) reduced Qm of the soil under the Wheat-Corn-Pea crop rotation system, and the application of NP plus organic manure (NPM) had a similar effect on Qm of the soil under the Wheat-Corn crop rotation system. The same in fertilization, the Wheat-Corn rotation and Wheat-Pea rotation systems significantly increased the contents of various forms of inorganic phosphorus, and the soils were higher in available P under long-term crop rotation than under continuous cropping, especially in Ca₂-P. Correlation analysis shows that Qm and phosphorus sorption index (PSI) were significantly negatively related to total phosphorus (T-P), Olsen-P, CaCl₂-P, Ca₂-P, Ca₈-P, Fe-P, Ca₁₀-P and organic phosphorus(p<0.01), and to occluded phosphorus(O-P, p<0.05), too, but insignificantly to Al-P. Soil organic matter(SOM) was found to be in extremely significant negative relations to Qm, PSI and maximum buffer capacity(MBC), but in positive one related to the degree of P sorption saturation(DPSS). Path analysis and stepwise regression analysis show that among the inorganic phosphorus fractions in calcareous Heilu soil, Ca₂-P contributed the most to Olsen-P.