Abstract: Based on the string structure of horizontal wells with multiple steam injection valves and in consideration of the variable mass flow of injected steam in horizontal wellbore as well as the impacts from throttle differential pressure of steam injection valve, a coupled reservoir-wellbore model of horizontal well with multiple steam injection valves were established and solved using an iterative method. On this basis, the outflow performance of horizontal wellbore with multiple steam injection valves were systematically studied. The results show that the pressure, temperature and steam quality in the tube of horizontal section gradually drop from the wellbore heel to toe in the multipoint steam injection process of horizontal wells. Moreover, the decrease of pressure and temperature is insignificant, while that of steam quality is more obvious. The steam injection rate and the throttle differential pressure of steam injection valve present the "U"-shaped asymmetrical distribution along the horizontal section. In addition, with the time increasing, the non-uniformity of steam injection rate along the horizontal wellbore is intensified, and the non-uniformity coefficient is becoming greater. The non-uniform injection of steam along horizontal wellbore can be slowed down to a certain extent by adjusting the drainage area of steam injection valves.