Aiming at the problem of selecting the number of neurons in the hidden layer of the Extreme Learning Machine(ELM),this paper proposes a search for the optimal number of neurons in the hidden layer by the particle swarm optimization algorithm(PSO),using the accuracy of the ELM model as the fitness function of the PSO(pso ELM).The algorithm was used to perform experiments on recognition of handwritten digital data set.Through comparison with the ELM by randomly setting the number of hidden neurons,the ELM opt...