Wireless sensor networks have widely application prospects in smart home system. Temperature and humidity are two important parameters of indoor environment, which affect the comfort of the room. In this paper, a temperature and humidity data acquisition system using wireless sensor networks based on TinyOS is presented. Wireless node module and sensor module are designed and TinyOS operating mechanism and development steps are analyzed. Underlying hardware drivers based on TinyOS and upper computer system are developed, forming a multi-hop network. Experimental studies show that this system is running well, and the expected design requirements are achieved.