Sensors are tiny computers with limited computational capability and physical resources. The implementation of secure protocols for sensor network is a big challenge. In order to provide high security for sensor networks, it is very important to choose a small, efficient and effective encryption algorithm as a security primitive. The TEA (Tiny Encryption Algorithm) is an efficient algorithm that requires little memory and resources. These features make the TEA a good candidate for security mechanism for sensors. In this paper we describe an implementation of the TEA algorithm on the platform of sensor networks. In our experiment, the data packets obtained from photo and temperature sensors are encrypted on the sensor node using the TEA algorithm. After that, they are sent to the base station by radio. The base station will receive the data packets and forward them to attached PC, where the data packets are decrypted and displayed. We also propose a particular approach to efficiently evaluate the performance of the TEA in terms of execution time on sensor nodes.