Abstract: Completing the lack data monitored by the sensors is a key problem of the information sensing process in the Internet of things. In order to solve this problem， a method was proposed， which can complete sensor data by using collaborative filtering. Considering that there are a lot of similarities among monitor data from sensors in the same area or from the one with different periods， properties of spacetime correlation between sensors were adopted in the proposed method. Different similarity evaluation was used to select similar sensors by classifying sensors with missing data in order to ensure the accuracy of the estimate. The results showed that using this method to estimate the missing data was better than other methods when there are large changes in the environment.

Key words: Internet of things, sensor, missing data, data completion, collaborative filtering