Phosphorus is one of the important elements in the ecosystem and plays a vital role in the process of life cycle. Inorganic phosphorus is a major form of phosphorus, usually in the form of phosphate ions. The rapid and efficient quantitative detection of phosphate ions has always been a hot research direction in the fields of clinical chemistry, pharmacology, biochemical analysis, industrial production and environmental pollution monitoring, but still facing some challenges in accuracy and convenient in some special circumstances. In present work, PAA-Ca(Ce) nanocluster fluorescent probes with good dispersibility and stability were synthesized by complexing with Ca²⁺ and Ce³⁺ using polyacrylic acid (PAA) as complexing agent. The reaction product between the probe and the phosphate ion was irradiated by 298 nm excitation light, and a linear graph was established based on the correlation between the peak intensity at the emission peak of 352 nm and the phosphate ion concentration. The experimental results show that the linear relation of the nanofluorescent probe with the (Ca²⁺+Ce³⁺) concentration of 37.575 mmol/L is y=1.09x+2.05, and the reliability range of fluorescence intensity is 13.5-66.91 mmol/L. Compared with molybdenum-antimony resistance spectrophotometry, this method has a higher recovery. The experimental results of inorganic phosphorus in rat serum verify the reliability of the method. The results above indicate that the fluorescence probe studied in this paper has good quantitative detection performance of phosphate.