Logic-information method is one kind of theories of quantification, and it is a comprehensive mathematical analyzing method that bases on symbolic logic, combinatory analysis, and mathematical statistics. By comparing the structural similarity of the objects, this method can evaluate the effect of some special factors. This article uses logic-information method to evaluate the fault sealing in Junggar Basin. This article filters the main geological indexes by logical calculation of the affecting factors of the standard objects (the typical fault whose sealing character is known). According to the affecting ability to the fault sealing of the geological indexes, some weightings are assigned to them. Then, object weightings of the standard objects can be calculated. Comparing these weightings with the fault sealing, the evaluating model of fault sealing can be built up. This model is used to evaluate ten chosen faults in Junggar Basin. The coincidence rate of the evaluating result and the real value is as high as 90%. This method can solve the following two problems in Junggar: why there is no large scale gas field in Wucaiwan region and why gas assembles only in the bottom wall of the fault in Hutubi gas field. Both of these prove that logic-information method can evaluate fault sealing efficiently.