The signals of network control system are transmitted in internet by the grouping form, which causes the problems such as time delay, packet dropout and so on in the transmission, as a result, in order to study the performance of the network system, this paper uses NS2 to set up network transmission model of network control system, and designs preferential queuing management algorithm by taking its preferential business grouping as research object. This algorithm is improved on the basis of DropTail algorithm, inherits the advantages of original algorithm, and contains business preference authentication and packet dropout selection mechanism. The validity of PDropTail algorithm is tested by using the two algorithms to do experiment for the analysis and comparison from the perspective of time delay, packet dropout and throughput. 