The invention discloses a disease recognition method based on a lightweight twin convolutional neural network. The method comprises the following steps of constructing a fine-grained lesion feature joint training model, wherein the fine-grained lesion feature joint training model comprises a data generator, the data generator is connected with a feature extractor, the feature extractor is connected with the twin convolutional neural network, and the twin convolutional neural network is connected with the feature discrimination network, training the fine-grained lesion feature joint training model, and generating a fine-grained lesion feature recognition model based on the fine-grained lesion feature joint training model with the minimum loss function value, and inputting the to-be-recognized image into the fine-grained lesion feature recognition model, and outputting a corresponding skin disease category. According to the method for carrying out positive and negative sample joint training based on the twin convolutional neural network, the model can extract more discriminative features, the conditions of small inter-class difference and large intra-class difference of lesion imagefeatures in an original data set are effectively relieved, and the feature discrimination capability of the model is enhanced.