The effective connectivity between the producer and injector in start-up period of SAGD has significant effect on production period. Field practice shows that the preheating time of conventional steam circulation is long while steam consumption and heat loss are large. In order to overcome these problems，evaluation experimental apparatus for solvent injection and soak was designed to evaluate the effect of viscosity reduction of xylene through sand pack soak by xylene injection at various flow rates. The results show that the viscosity of heavy oil decreased significantly with the increasing of xylene solvent content without asphaltene precipitation production，and the mobility of oil was enhanced. When the injected solvent content reaches a certain value，viscosity is no longer reduced. The oil phase permeability increases with the increasing of flow rate of the solvent，but the range of increase gradually decreases. After solvent soaking with pressure，the solvent spreads around to improve the sweep area and expand the flowing channel，and the oil permeability will be increased further. The application in a certain block of A oilfield in Xinjiang shows that circulation and preheating time in the solvent soaked well group significantly decreases by about 60 d and the injected steam volume decreases by about 4 000 m3. The connectivity degree between the producer and injector is about 85% when ES-SAGD production begins. Numerical simulation and pilot test present that solvent injection of ES-SAGD in start-up period can shorten the preheating time of steam circulation，reduce the injection steam volume，make even preheating between producer and injector and improve the preheating efficiency and economic benefit.