The high-order harmonic component of a 1 GHz modulated sinusoidal wave optical signal is injected into the directly modulated laser, and the interaction between the intensity of the light field and the carrier concentration forms the photocurrent. The photocurrent is then converted into a microwave frequency multiplication signal at the radio frequency (RF) port of this directly modulated laser. In the experiment, the feedback control the directly modulated laser wavelength and thus the automatic locking of the laser are realized by the powe rvariance of the frequency multiplication signal detected at the RF port. The microwave frequency multiplication signals at 10 GHz and 12 GHz are generated without photodetectors. Compared with those by the injection locking scheme without an automatic locking loop, the microwave frequency multiplication signals by automatic locking are more stable. The power fluctuation is stable at 2 dB within 10 min, and the phase noise deterioration at 10 kHz is as little as 2.2 dB. The produced largest frequency doubling number of microwave frequency multiplication signals depends on the maximum modulation rate of the directly modulated laser.