The ZnMgO/ZnO ultraviolet band Distributed Feedback（DFB）semiconductor laser is simulated and designed by using the Transfer Matrix Method（TMM）.A peak wavelength of 364.8nm is obtained when the duty cycle is 0.5

the grating period is 92.5nm

and the height of the grating is 65 nm.By changing the thickness of active layer

the influence of different active layer thickness on the performance of the laser is analyzed.The numerical simulation results indicate that when increasing the thickness of the active layer

the threshold current is increased as the limitation on the carrier is weakened.When reducing the thickness of the active layer

the limiting effect of the waveguide layer on the photon decreases

which result in a higher threshold current and a lower output power.Therefore

the proper selection of active layer thickness can improve the performance of DFB laser.