This paper obtained the U-Pb age data with LA-ICP-MS in fine-grained zircons from the part of the rock of Xikou composite intrusives. The dating result of gneissic metacrystal medium monzonite granite of Tiankengli is 452.6±7.8 Ma. The dating result of medium-grained granite of Jijiaoli is 161.2±2.9 Ma and 168.6±3.7 Ma. The results with previous ages studies show that the Xikou composite intrusive was a multiple-intrusive rock foundation in Shanghang area of the southwestern Fujian, and was formed in three stages at least. That is, 440~460 Ma, Caledonian period; 394~274 Ma, Variscan period; and 120~169 Ma Yanshanian period. However, the Yanshanian period maybe divide into middle and late period. In the first stage, Caledonian period, formed monzogranite and quartz porphyry. In the second stage, Variscan period, formed medium—fine grained porphyraceous granite and porphyritic granite. In the third stage, Yanshanian period, formed medium—fine grained biotite granite and syenogranite. However， 120~169 Ma was the main magmatic period. This stages of the Xikou composite intrusive was the same as the large-scale magmatic activity in eastern China, and its diagenesis may be related to lithosphere extensional tectonics.