A novel type of lower extremity exoskeleton with series-parallel topology was described. Position analysis of a simplified leg was conducted to provide a basis of the kinematic accuracy reliability. Considering both assembly-machining errors and driving errors, the fuzzy reliability of kinematic accuracy was obtained based on the fuzzy probability theory. With a set of optimized length parameters and joint ranges of motion given, the fuzzy reliability of space distribution and the average fuzzy reliability were respectively calculated and shown in figures. These analyses of kinematic accuracy reliability provide a unique method to judge, analyze, and design exoskeleton mechanisms.