With the rapid development of Internet, short videos draw more and more attentions nowa- days. Due to the small scale of short videos, image-level coding scheme can be applied to improve compression efficiency. In this paper, we propose a densely connected unit based loop filter for short video coding in H.266/VVC. In the proposed loop filter, the densely connected units are specially designed to extract feature maps, and fully decompose videos. By densely connection between layers, the designed units can reuse feature maps, and re- duce the redundancy of features. Meanwhile, the proposed loop filter has the light weight, which can recover short videos at image level fast. Moreover, the proposed loop filtering network is embedded into VVC to replace the original sample adaptive offset (SAO) and adaptive loop filter (ALF), which saves bits cost and lowers the complexity of coding. The experimental results show that the proposed loop filter, compared with H.266/VVC, can achieve 4.50 % bit-rate reduction in AI mode at average. In RA mode, the proposed loop filter can also achieve 2.61 % bit-rate reduction at average.