In order to realise effective target detection with a large baseline radar network interfered by a single radiation source, an adaptive processing method derived from traditional principal component analysis (PCA) and array signal processing theory is proposed in this study. First, the signal model for target detection with a large baseline radar system in an interference environment is established. Second, based on the characteristics of the signal model, an adaptive suppression method composed of high‐precision delay alignment and modified PCA is proposed. Finally, the effectiveness of the method in a typical environment is verified by simulation. The results show that this method can accumulate target energy effectively and realise reliable detection in such case, which has great application prospects.