Based on the triune Chinese function word usage knowledge base (CFKB), the rule-based method, CRF (conditional random field) model and GRU (gated recurrent unit) are adopted to automatically recognize the usages of auxiliary “DE”, and the accuracy rates are 34.4%, 77.5% and 81.3% respectively. In order to improve the accuracy, some usages of auxiliary “DE” are combined and formed coarse-grained usage. The accuracy of CRF achieves 81.8%, and the accuracy of neural network model achieves 84.5%. It is expected that the recognition result of auxiliary “DE” can improve the performance of other NLP task.