Title: So-TVAE: Sentiment-oriented Transformer-based Variational Autoencoder Network for Live Video Commenting. Abstract: Automatic live video commenting is with increasing attention due to its significance in narration generation, topic explanation, etc. However, the sentiment consideration of the generated comments is missing from the current methods. Thus, in this paper, we introduce and investigate a task, namely sentiment-guided automatic live video commenting, which aims to generate live video comments based on sentiment guidance. To address this problem, we propose a Sentiment-oriented Transformer-based Variational Autoencoder (So-TVAE) network, which consists of a sentiment-oriented diversity encoder module and a batch-attention module. Specifically, our sentiment-oriented diversity encoder elegantly combines VAE and random mask mechanism to achieve semantic diversity under sentiment guidance, which is then fused with cross-modal features to generate live video comments. Furthermore, a batch attention module is also proposed in this paper to alleviate the problem of missing sentimental samples, caused by the data imbalance, which is common in live videos as the popularity of video varies. Extensive experiments on Livebot and VideoIC datasets demonstrate that the proposed So-TVAE outperforms the state-of-the-art methods in terms of the quality and diversity of generated comments. Related codes will be released.