Aiming at the problem that the stochastic connection of enterprises may lead to the decrease of network stability and operational efficiency in the evolution stage of supply chain network， an improved connection algorithm of supply chain network based on Expectation Maximization （EM） algorithm was proposed. Firstly， the number of edges of network nodes was added to the algorithm as a new parameter to determine the number of edges possessed by new nodes in the supply chain network more accurately. Secondly， with the number of edges determined， residual edge connection rules was introduced to enhance the selectivity and differentiation of nodes. Finally， by ensuring the smooth operation of the enterprise nodes newly connected to the network， the influence of different initial edge numbers on the network evolution was studied. Simulation results show that compared with the EM algorithm， the proposed improved algorithm only needs 80 iterations to obtain stable results， and the number of connected edges is stable around 4 within the network scale of 1 000 nodes， which matches the evolution process of the actual supply chain network. It can be seen that the proposed algorithm is obviously better than the original EM algorithm in fitting performance of the actual supply chain network.