Personalized human activity recognition (HAR) on wearable sensor data is crucial for healthcare, industry and sport. Personalized HAR has two challenges: very few high-quality labeled personalized data and limited terminal computing resource. Most previous domain adaptation models ignore the transfer efficiency on the terminal, which is also one criterion of Artificial Intelligence of Things. Therefore, we propose a fast transfer HAR, FastTrans, to improve the efficiency and get a trade-off with recognition effectiveness. A fusion feature extraction module is designed to learn multi-scale features on the improved hybrid loss. The proposed heuristic parameter estimation method learns the approximate solutions of the classification weights in FastTrans by scanning the adaptation data only once. Besides, an efficient time series data augmentation is proposed as a plugin for dataset variety. The results on benchmark datasets show the dramatically competitive performance of FastTrans on transferring efficiency with close accuracy to other models.