To overcome the shortcomings of wired temperature and humidity measurement system, a temperature and humidity measuremet system based on wireless sensor networks was designed. the components of the system and its working principle were described in detail. Its nodes use a digital temperature and humidity sensor SHT15 for data collection, wireless transmission chip CC1100e for data short-range wireless transceiver and the wireless network, and AT89S52 microcontroller for controlling core. Nodes communicate with the background host through serial interfaces. The system can achieve environmental temperature and humidity dynamically and comprehensive real-time monitoring. Node has a dual function as terminals and routers, in addition to data processing, but also for other nodes to forward the temperature and humidity data storage, management, and integration, and taking in collaboration with other nodes to complete some specific tasks. The system has some advantages such as low cost, low power consumption and small size, which has a good application prospects.