A novel tunable laser based on Fabry-Perot (F-P) laser self injection locking is proposed. A single longitudinal mode is filtered from the multi-longitudinal modes of the F-P laser by the F-P etalon and injected back into the F-P laser to suppress side mode. We can change the spectrum of the F-P laser by tuning the driving current rapidly, and realize a wide tuning range of the wavelength by virtue of the vernier effect between the varying spectrum of the F-P laser and the stable spectrum of the F-P etalon. The static characteristics of the tunable laser are studied and 18 sets of single longitudinal modes are available. The tuning range of wavelength is from 1535.2 nm to 1548.68 nm, and the side mode suppression ratio of the single longitudinal mode is 40 dB. The power difference of each wavelength is less than 15 dBm and the frequency interval is 100 GHz. A wavelength tuning experiment is carried out, and the tuning time for different wavelengths ranges from 60 ns to 100 ns. The feasibility of the scheme is verified.