Abstract: A wellordered mesoporous material P-SBA-15 functionalized with phosphoric acid group was prepared by postsynthetic method. Characterizations by power X-ray diffraction (XRD), infrared spectroscopy (IR), as well as nitrogen sorption（BET）were carried out to understand the physical properties of P-SBA-15. The results show that the structure of P-SBA-15 remains that of silica mesoporous material SBA-15, and the specific surface area and the mesopore size of P-SBA-15 are 605.45m2/g and 5.576nm ( np/n si =5% for example), respectively. Synthesis of iso-propyl undecylenate over the P-SBA-15 catalysts was studied in order to investigate the catalytic properties of mesoporous molecular sieve P-SBA-15. Compared with liquid acid and microporous zeolite catalysts, the P-SBA-15 is the best one among the solid acids for esterification reaction. Reuse of P-SBA-15 indicated this catalyst has high stability under esterification conditions.