The invention discloses an optically controlled phased array radar system based on wavelength routing. N tunable semiconductor lasers emit multiple paths of optical wave signals different in wavelength; microwave signals are loaded and modulated through respective modulators, transmitted to a first array waveguide grating router, transmitted to a second array waveguide grating router through a delayed linear array and transmitted to N semiconductor detectors for demodulation; the semiconductor detectors emit the demodulated microwave signals through an antenna. The tunable semiconductor lasers are used to change the wavelengths for switching the delayed linear array, so that the use of a large amount of optical switches is avoided; with an integrated optics method, an overlapping problem of fiber Bragg gratings is solved, the two array waveguide grating routers and the delayed linear array are integrated on the same substrate, and the precision of the delay line length is guaranteed, so that the stability of the system is improved, the cost is reduced, and the system has the advantages of small size, low loss, light mass, high precision, electromagnetic interference resistance and the like.