Cycloid planetary gear plays an important role in precision transmission. Accuracy control of transmission is an extra crucial requirement for design and manufacture. Firstly presented a mathematical approach for precision analysis on cycloid gear, it enable predict mesh stiffness, backlash and angular transmission error with consideration of manufacture tolerance, elastic deformation in cycloid gear. Secondly, the solution was developed for angular transmission error analysis in K-H-V reducer, in which includes effect from bearing (stiffness and initial mounting conditions), crank shaft (offset error and flexibility). Finally, experimental study was conducted for validation which showed good agreement with simulation.