The phase-shifting Grating-Slit test has advantages of large measurement dynamic range when using with spatial light modulator (SLM) to generate the illuminating. But the rotary slit in the test does reduce the measuring speed and may cause measurement error if it's not aligned properly with the grating. Thus, a new modulating apparatus is proposed to replace the rotary slit used in the Grating-Slit test. In addition, a pellicle beam splitter is used to make the on-axis measurement possible and the measurement error from misalignment is greatly reduced. With a micro liquid crystal display generating and switching the direction of the illuminating grating, we can simultaneously interlace the tip-tilt direction alignments during measurement.