Free space optical communication based on orbital angular momentum (OAM) is considered to be a promising next generation communication application. In order to realize OAM multiplexing communication, one of the key technologies is the detection of vortex beam’s OAM at the receiving end. Using convolution neural network method, a theoretical scheme for accurate identification of OAM of dual-mode vortex beams is studied. The OAM beam can provide two controllable degrees of freedom, e.g. the topological charge number l and the proportional coefficient n. The relationship of the training sample resolution or the number associated with the accuracy of the model is presented. The recognition accuracy is closely related with the quantum number l of the OAM, and the proportional coefficient n. This studies show that when l ranges from 1 to 10, and n varies from 0.01 to 0.99, the recognition accuracy rate of OAM is 100%.