Few-shot object detection (FSOD) can effectively improve object detection performance with limited training data, attracting increasing interest from researchers. Due to the limited sample size, there is often a large variance in the learned features, resulting in deviating from the class center and being confused with other classes. People are often able to accurately identify few-shot objects based on discriminative information. Motivated by it, we propose a discriminative prototype with dual decoupled contrast learning (DP-DDCL) method to address the issue of limited training data in FSOD. By introducing domain knowledge comprising the CLIP and attribute knowledge graph to obtain explicit and implicit semantic and visual information, we construct a novel discriminative prototype that enhances the representation of different classes (especially few-shot samples). Simultaneously, dual decoupled contrast learning consists of the decoupled of positive and negative samples, and the decoupled of discriminative prototype and instance contrast learning is proposed. It makes samples of the same class cluster around their respective class prototype while maintaining a clear semantic boundary between different classes. Extensive experiments demonstrate the efficacy of our method, surpassing the current state-of-the-art in any-shot and all-data splits, with maximum performance gains of up to +9.15% on the standard PASCAL VOC benchmark and +2.5% on the challenging COCO benchmark.