In order to increase the exposure contrast of the holographic grating exposure system, and depress the exposure interference fringe drifts caused by the environmental changes, a method of interference fringe locking by grating-shifting is proposed. The beam splitter grating is used to split the beam from laser source and adjust the phase of the interference fringe. The phase changes of the interference fringe are measured indirectly by Moire fringe. The best detection locations of the two photoelectric detectors are given. The parameters design method of the beam splitter grating is presented by combining the function of splitting beam and regulating phase. The controller is designed aiming at the characteristic of the grating exposure. The phase-regulating performances of the beam splitter grating and the piezomirror are contrasted theoretically. The experiment results illustrate that the low-frequency drifts of the interference fringe are depressed at a sample frequency of 500 Hz. The value of the phase locking is below 0.13 rad (3σ), namely the fringe drift is below ±0.021 period. The exposure interference fringe can be timely and effectively locked by this method, and the exposure contrast is improved. The tilt of the beam splitter grating has little effect on fringe′s period. Besides, the phase regulating performance is only relevant to the parameters of the beam splitter grating, which is convenient to the design of the optical layout.