The invention provides a low-altitude flyer detection method based on a compressed SSD, and relates to the technical field of target detection. The channel pruning algorithm is adopted to compress the model, and the detection speed of the model is increased. The method comprises the following steps: firstly, adding a batch normalization layer in a basic model, and introducing a scale factor for each channel; then, a scale factor is jointly trained, so that the numerical value of the scale factor is associated with the importance of the channel. And finally, judging the importance of the channels by measuring the size of the scale factor, and cutting off the channels with low importance. The performance of each aspect of the compressed model is superior to that of the original model, the network structure of the model is more refined, the size is greatly reduced, the operation speed is higher, and a higher detection speed can be obtained. According to the channel pruning method adopted by the invention, the importance of each channel is measured, so that the influence of the pruned channels on the precision of the model is small, and therefore, the precision of the optimized model is close to that of the original model.