Abstract: Due to the lack of state evaluation mechanism in traditional fault detection technology and the large detection error, a fault detection technology based on nonlinear state estimation and long delay packet loss network is proposed, which can reduce detection error. According to the detection principle, the design of nonlinear network fault state estimation process, so as to construct a long delay fault condition assessment mechanism, according to the analysis of long time delay signal feature evaluation results; set reasonable analysis rules, construct the packet loss fault state evaluation mechanism, combined with obeys Bernoulli distribution information, analysis of packet loss signal characteristics. The fault detection is completed according to the result of signal characteristic analysis. The experimental results show that the detection error of the technology is up to 0.1, and it can satisfy the constraints of the actual error index.