To study the SAGD development mode with the combination of vertical and horizontal wells in Du 84 block of Liaohe oilfield and improve oil displacement efficiency, physical simulation system with three-dimensional proportion of high-temperature and high-pressure is established and experiment is carried out. Through recording and processing real-time experiment data of temperature and pressure of survey points, the temperature field diffusion regularity within the model in the ideal state is achieved and the steam overlap phenomenon is found by observing the temperature field. Combining the curve of instantaneous oil recovery and water cut, the production of SAGD with the combination of vertical and horizontal wells is divided into: steam chamber development stage, steam thermal connecting stage, thermal fluid discharge stage, production decline stage. Mastering the changes of various parameters of the production curve and phenomenon that can appear will provide theoretical and practical significance for guiding reasonable heavy oil development and development of technique policy for vertical-horizontal SAGD mode.