In this paper, a new electrical tuning method for an external cavity semiconductor laser is presented. The continuous tuning condition is theoretically and experimentally analyzed. A single PZT (Bimorph) is used to change both the cavity length and the grating angle. The cavity structure is so designed that the continuous tuning condition can be satisfied. The scanning angle of the bimorph is about 1°. As wide as 15 nm a tuning range and a 50GHz continuous range (without mode hopping) are obtained.