A method for quasi-synchronous tuning of laser wavelength or frequency of grating external-cavity laser and a corresponding laser are provided. A grating or mirror is rotated around a quasi-synchronous tuning point (Pq) to achieve the quasi-synchronous tuning of frequency selections by grating and resonance cavity, wherein, on the xOy coordinate plane, from the perspective of actual physical space of the laser, the rotation center Pq(xq, yq) satisfying the quasi-synchronous tuning condition can be considered as being extended from the rotation center P0(x0, y0) under the conventional synchronous tuning condition to the region enclosed by two parabolas near P0. According to the present disclosure, approximately-synchronous tuning of laser is achieved with simple and flexible designs.