The ability to learn new concepts while preserve the learned knowledge is desirable for learning systems in Class-Incremental Learning (CIL).Recently, feature expansion of the model become a prevalent solution for CIL, where the old features are fixed during the training of the new task while new features are expanded for the new tasks.However, such task-specific features learned from the new task may collide with the old features, leading to misclassification between tasks.Therefore, the expanded model is often encouraged to capture diverse features from the new task, aiming to avoid such collision.However, the existing solution is largely restricted to the samples from the current task, because of the poor accessibility to previous samples.To promote the learning and transferring of diverse features across tasks, we propose a framework called Task-Agnostic Guided Feature Expansion (TagFex).Firstly, it captures task-agnostic features continually with a separate model, providing extra task-agnostic features for subsequent tasks.Secondly, to obtain useful features from the task-agnostic model for the current task, it aggregates the task-agnostic features with the task-specific feature using a merge attention.Then the aggregated feature is transferred back into the task-specific feature for inference, helping the task-specific model capture diverse features.Extensive experiments show the effectiveness and superiority of TagFex on various CIL settings.