Title: STMT: A Spatial-Temporal Mesh Transformer for MoCap-Based Action Recognition . Abstract: We study the problem of human action recognition using motion capture (MoCap) sequences. Existing methods for MoCap-based action recognition take skeletons as input, which requires an extra manual mapping step and loses body shape information. Therefore, we propose a novel method that directly models raw mesh sequences which can benefit from the body prior and surface motion. We propose a new hierarchical transformer with intra- and inter-frame attention to learn effective spatial-temporal representations. Moreover, our model defines two self-supervised learning tasks, namely masked vertex modeling and future frame prediction, to further learn global context for appearance and motion. Our model achieves state-of-the-art performance compared to skeleton-based and point-cloud-based models. We will release our code and models.