To solve the problem of the design of classifier in net work threat detection, we conduct a simulation experiment for the parameters optimal on least squares support vector machine (LSSVM) using the classic PSO algorithm, and the experiment shows that uneven distribution of the initial particle swarm exerts a great impact on the results of LSSVM algorithms classification.This article proposes an improved PSO-LSSVM algorithm based on Divide-and-Conquer (DCPSO-LSSVM) to split the optimal domain where the parameters of LSSVM are in.It can achieve the purpose of distributing the initial particles uniformly.And using the idea of Divide-and-Conquer, it can split a big problem into multiple sub-problems, thus, completing problems modularization.Meanwhile, this paper introduces variation factors to make the particles escape from the local optimum.The results of experiment prove that DCPSO-LSSVM has better effect on classification of network threat detection compared with SVM and classic PSO LSSVM.