Abstract: An accurate costume structure design is based on the “Human Body-Costume” System, the most important and complex part in men’s garment is the design of “Armhole-Sleeve” part. This structure influences the form of Shoulder-Sleeve and wear comfortbility, as well as the mobile harmony of both human upper body and arms. The article analyses the main structural factors which influence the armhole-sleeve part in the rational men’s garment and makes a research into arm shape of human body and conditions of how both the armhole-sleeve and the arm shape well cooperate each other. Traditional body measuring can not accurately express the upper body spatial position relationship, however, this article makes an amendment to the arm measuring method. It suggests a new position and a new method to measure the arm of human body and it also generally classifies the outline of men’s arm. It ascertains the conditions of inharmony between the arm and the structural form of sleeve in men’s garment which leads to defects in sleeve. Through utilizing new parameters of structure in combination with the morphology of human body, the author makes a rational and effective plan to structural allocation, therefore, a static harmony between the outline of arm and the ready-made sleeve of men’s garment has been achieved, the happening of defects in sleeve has been decreased.