As one of the key technologies in wireless networks, time synchronization is the supporting technology of factory automation wireless network that guarantees high reliability and high real-time. The high rate and simply effective topology of IEEE 802.11 make it become the best protocol for wireless network of factory automation. This paper first analyzes the importance of clock synchronization precision for high reliability and high real-time in factory automation and proves that high time synchronization precision is the important goal for wireless network in factory automation. Then it designs and realizes the high precision time synchronization method of wireless network for factory automation based on TDMA mechanism on commercial IEEE 802.11 hardware. The high-precision time synchronization method includes three algorithms that are clock skew measurement, clock skew prediction, and clock skew compensation, which are interlocked in one cycle of superframe of TDMA mechanism for high precision of time synchronization. Experiments show that through measurement, prediction and compensation, the time synchronization precision is improved obviously relative to the traditional two-way time synchronization algorithm. The high reliability and strong adaptability of this method adapt to the factory environment, and the high precision of time synchronization is helpful to realize the TDMA timeslot schedule in microsecond of wireless network for factory automation.