Abstract: The double horizontal well SAGD technology requires that the horizontal section trajectory of steam injection well remains parallel to that of production well. If the horizontal section has relatively large deviation in trajectory, the thermal connection between injection-production wells will become relatively difficult, the cyclic preheating time will increase, and the production effect of SAGD well group will be affected. In order to evaluate the wellbore trajectory quality of such type of well group in a quantitative manner, the following 4 new concepts which can be used to indicate the wellbore trajectory quality of SAGD double horizontal well have been brought forth , production well target area encountering rate, steam injection well vertical distance pass rate, steam injection well horizontal deviation pass rate and double horizontal well parallelism. On the basis of the special geometrical relation between two horizontal wells and in consideration of the permissible error range of target area, the analytical calculation model for the above-mentioned concepts has been derived. The analysis on actual cases indicates that, these pass rates can evaluate the grade of horizontal section trajectory quality of SAGD double horizontal wells in a quantitative manner, and is relatively consistent with the situation reflected by trajectory figure.