WirelessHART is becoming widely used industrial communication standard due to its features such as low cost, low power consumption and strong interoperability. As a research hotspot, time-sync is one of key technologies for WirelessHART networks. Firstly this study summarizes the existing time-sync methods. Secondly, by means of building slot timing model, this study focuses on time slot setting up, active time-sync and passive time-sync processes for WirelessHART network time-sync. The calculation method of time cycle for keep-alive data packets used for keeping time-sync is proposed. The keep-alive data packet cycle of 30 sec is proved reasonable in WirelessHART standard. Finally, test platform is set up using the self-development WirelessHART communication module WH-M and the time-sync mechanism of WirelessHART network is realized. The time-sync error of testing data is small enough to meet the time demand of TDMA in industrial communication fully.