The performance of reactive power control system seriously affect the normal operation of wind farm. However, typical system architecture of reactive power control system usually contains several hierarchies and the communication network of the whole system is very complicated. So, the assessment of reactive power control system should take the communication network between these hierarchies in consideration inevitably. In this paper, instead of using a time delay to simulate the data transportation delay, a new method to model the network topology and data link layer is proposed. With this method, the communication network model, the reactive power control strategy as well as the wind farm model are all established in the same MATLAB/Simulink environment. Then the communication network performance such as end to end delay, node workload, communication protocol etc. can be evaluated and the influence of communication network to the reactive power control system can be analysed in one environment. In final, the effectiveness of this modelling method is validated by model simulation of the reactive power control system integrated with communication network.