Abstract: An external cavity laser and a tuning method therefor are provided. The external cavity laser includes a gain chip, and a tunable reflector. The tunable reflector includes a main waveguide, a beam splitter, a first branch waveguide, a first photonic crystal modulator, a second branch waveguide, and a second photonic crystal modulator. The beam splitter is configured to equally split the optical signal transmitted by the main waveguide into a first optical signal and a second optical signal and is configured to transmit the first optical signal to a first branch waveguide and the second optical signal to a second branch waveguide. A first photonic crystal modulator is configured to tune the first optical signal transmitted by the first branch waveguide. A second photonic crystal modulator is configured to tune the second optical signal transmitted by the second branch waveguide.