Continual Few-Shot Relation Learning (CFRL) aims to learn an increasing number of new relational patterns from a data stream. However, due to the limited number of samples and the continual training mode, this method frequently encounters the catastrophic forgetting issues. The research on causal inference suggests that this issue is caused by the loss of causal effects from old data during the new training process. Inspired by the causal graph, we propose a unified causal framework for CFRL to restore the causal effects. Specifically, we establish two additional causal paths from old data to predictions by having the new data and memory data collide with old data separately in the old feature space. This augmentation allows us to preserve causal effects effectively and enhance the utilization of valuable information within memory data, thereby alleviating the phenomenon of catastrophic forgetting. Furthermore, we introduce a self-adaptive weight to achieve a delicate balance of causal effects between the new and old relation types. Extensive experiments demonstrate the superiority of our method over existing state-of-the-art approaches in CFRL task settings. Our codes are publicly available at: https://github.com/ywh140/CECF.