The invention discloses a method for accelerating multi-exit DNN (Deep Neural Networks) reasoning by a heterogeneous processor under edge computing, which comprises the following steps of: firstly, respectively counting the computing cost of each layer of a deep neural network on a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit) under different loads, the classification capability of each layer exiting a branch exit in advance and the intermediate data volume of each network layer; then analyzing the data to obtain an optimal parallel combination model for distributing each layer of the deep neural network to a CPU (GPU) processor under a specific load condition; and finally, the load conditions of the CPU and the GPU and the current computing power are monitored and analyzed on a terminal device on line, a deep neural network reasoning task is segmented with the purpose of minimizing reasoning time delay, task blocks are distributed to the GPU and the CPU respectively, and finally a reasoning acceleration framework based on a heterogeneous processor is formed. According to the method, the reasoning flexibility can be improved, the accuracy is ensured, the reasoning total time delay is reduced, and the real-time and high-precision requirements of edge intelligent application are met.