Abstract: The paper adopted the lineation-on-body method to measure the change of skin caused by hands free movement,deduced the change rule of each parts through the mean-analysis and its relationship with garment structure.Further correlation analysis and component analysis were done of the back width because the analytical results displayed that the change of back width was notable and tended to expand.It was found through further correlation and factor analyses that the change of the back width can be attributed to three main factors,that is,arms forward movement,raising up and outward movement,and raising up and backward movement,and it is the forward movement that results in the enlargement of the back width,which should be taken careful consideration when studying the exercise comfort and garment ease.