With the rapid proliferation of IoT devices, device management and network security are becoming significant challenges. Knowing how many IoT devices are in the network and whether they are behaving normally is significant. IoT device identification is the first step to achieve these goals. Previous IoT identification works mainly use supervised learning and need lots of labeled data. Considering collecting labeled data is time-consuming and cannot be scaled, in this paper, we propose an IoT identification model based on semi-supervised learning. The model can differentiate IoT and non-IoT and classify specific IoT devices based on time interval features, traffic volume features, protocol features and TLS related features. The evaluation in a public dataset shows that our model only needs 5% labeled data and gets accuracy over 99%.