In Chinese, writing is a basic competency that pupils should possess. But it is still challenging for teachers to improve pupils' writing abilities. Therefore, this study proposes an intelligence-based cognitive diagnostic feedback strategy to improve pupils' writing ability and writing learning quality by analyzing their writing performance, epistemic network structure, and learning engagement. Thepupils are randomly divided into an experimental group (N = 28) and a control group (N = 28). The experimental group adopts the ICDF strategy, while the control group adopts the WS-TF strategy. The results showed that the I-CDF strategy improved the pupil's writing scores and learning engagement. In addition, the results of the epistemic network analysis showed that the pupils using the ICDF strategy focused on dynamic descriptions such as action, psychology, and environmental changes in vocabulary use, and the epistemic network structure was more complex than the control group. The interviews showed that the pupils in the experimental group were highly satisfied with I-CDF strategy.