To simultaneously simulate the flow behavior in the reservoir and horizontal wellbore, it is necessary the developing of a coupled model integrating both reservoir domain and horizontal wellbore domain. This paper investigates the transient flow behavior of horizontal wellbore and reservoir using a two phase coupled model. All the variables for both reservoir and wellbore domains are solved simultaneously, so that the results can reflect the flow characteristics and interactions between the reservoir and horizontal wellbore. The results show that the proposed coupled model can reveal the finite conductivity features of the horizontal wellbore. The influx and its effect are actually non-uniform distributed. A case study was conducted and analyzed in this paper.