Due to state explosion problem, signal transition graph based asynchronous circuit synthesis cannot handle large specifications. To overcome this problem, we propose two control signal sharing methods by using the delay information of data-path circuit. Since the number of states is exponential with the number of signals in the synthesis, the reduction of signals by sharing can reduce the number of states in exponential order. They are carried out at the control of data-path operations which is represented as a control flow graph description, without sacrificing the critical path delay of data-path circuit. Experimental results are encouraging in that a number of control signals can be shared by our methods.