Abstract: Hypophosphatemia is a common metabolism disease in humans. Fibroblast growth factor 23 (FGF23) inhibits phosphate reabsorption by targeting on the renal tubules. FGF23^C-tail contains 73 amino acids from C-terminus of FGF23, serves as an inhibitor of FGF23, and can increase phosphate reabsorption. Therefore, FGF23^C-tail is an important drug for hypophosphatemia. In this paper, we constructed a fusion protein of FGF23^C-tail with HSA, and investigated the expression of the fusion protein in the Pichia pastoris system. The recombinant gene was constructed by fusion PCR. A high-yield strain was selected by G418 resistance and fermentation yield, and the expression yield was 43.7 mg·L^-1 in flask. In 5 L fermenters, the highest expression yield could reach 265.6 mg·L^-1. FGF23^C-tail-HSA could be used as an inhibitor for FGF23, and could significantly increase blood phosphorus levels in rats. The procedures for care and use of animals were approved by the Ethics Committee of YiChun University. This paper provided a basis research for further studying physiological activity of FGF23^C-tail-HSA.