An enzyme-amplified lanthanide luminescence assay of alkaline phosphatase was described. Optimization of important factors in this assay was studied. Improvement of stability of signal/noise ratio by using methyl silicon oil (I) was first reported. The sensitivity and the accuracy of the assay were 4 U/L and ＜10% respectively. The concentration range corresponding to 10% precision was 2.00～3.02×10² U/L. The activity of alkaline phosphatase in serum was also detected and the recovery was 93%～95%. 5-fluorosalicyl phosphate was synthesized and used as substrate.