Abstract: We have introduced the concepts of the reaction-reversal transformation and the relative symmetry (the invariance under the union transformation of reaction reversal and point-parity),since there are no any point symmetry in sigmatropic reactions. By means of such way,the symmetry and corresponding selection rules of the sigmatropic and some other reactions can be explained more perfectly. However there are some defects in our pervious argument, too. In this paper, the symmetry of sigmatropic reaction are restudied, some suposses are modified and some unnecessary supposes are deleted. Therefore such theorm will be described more tersely and intrinsically.