Abstract: Because of the signal instability in the mobile network environment, the paper proposes to divide the collaboration elements into different granularities according to the network status so as to reduce network load. In order to maintain the consistency of the shared documents in the new collaboration environment and improve the algorithm efficiency, the linear document model is mapped to the tree model. Outbuffer and in-buffer are added to merge and handle operations before broadcasting, and to decompose the operations after receiving. The address space transformation strategy is adapted for the new model space. In this paper, a prototype system Co-UEditor which can support multi-granularity collaboration in the Android platform is developed based on the open-source text editor package UEditor, which validates the whole strategy.