Title: Network Pruning Optimization by Simulated Annealing Algorithm. Abstract: One critical problem of large neural networks is over-parameterization with a large number of weight parameters. This becomes an obstacle to implement networks in edge devices as well as limiting the development of industrial applications by engineers for machine learning problems. Plenty of papers have shown that the redundant branches can be erased strategically in a fully connected network. In this work, we reduce network complexity by pruning and structure optimization. We propose to do network optimization by Simulated Annealing, a heuristic based non-convex optimization method which can potentially solve this NP-hard problem and find the global minimum for a given percentage of branch pruning given sufficient amount of time. Our results have shown that Simulated Annealing can significantly reduce the complexity of a fully connected neural network with only limited loss of performance.