With the increasing popularity of computer vision and deep learning, the use of convolutional neural network in loop closure detection has become more and m‐ore popular In this paper, the influence of the structure and depth of Convoluti‐onal Neural Network on the performance of loop closure detection algorithm is verified by comparing the convolutional descriptors extracted from different laye‐rs of Convolutional Neural Network. Group‐based experiments were carried out on three open data sets respectively to draw the curves of precision‐recall rate, compare performance parameters, and obtain the robustness of the convolutiona‐l image descriptors of different layers for scenes of seasonal change, lighting ch‐ange and multi-interference, so as to find out the appropriate number of netwo‐rk layers to complete loop closure detection. According to the experimental res‐ults on the data set, the experimental conclusion is drawn.