The invention discloses a target detection method, a target detection model and a target detection system based on a cascade detector. The target detection method comprises the following steps of S1,training the target detection model by adopting a training data set with a target label; S2, inputting a to-be-detected picture into the trained target detection model, and performing feature extraction, upsampling and feature fusion to obtain feature maps P2, P3,..., Pn with different sizes; S3, predicting according to the feature map Pn to obtain a target position Bn and a category Cn; extracting corresponding features from the corresponding feature map Pi-1 according to the target position Bi for target prediction to obtain a target position Bi-1 and a category Ci-1, i = 3-n; S4, taking thetarget position B2 as a final prediction result. According to the invention, through the multiple iterative regression prediction of the the target candidate box, the target position with more accurate prediction is obtained, the target detection precision is improved, and the detection accuracy is higher.