The laser-controlled micro-crystallization technology for hydrogenated amorphous silicon aH-Si thin films is studied. The aH-Si thin films on crystalline silicon (c-Si) are annealed by YAG laser with the frequencies of 4, 8, 10, 12, 15 Hz, while keeping the laser power, pulse width and facula unchanged. The influence of laser frequency on aH-Si thin film crystallization is studied. The analysis of aH-Si thin film microstructure and surface morphology is conducted using X-ray diffractometer (XRD) and atomic force microscope (AFM). The results show that the grain size of the aH-Si thin film becomes larger with the laser frequency increasing from 4 Hz to 10 Hz, and decreases with the laser frequency keeping increasing from 10 Hz to 15 Hz. The maximum average grain size reaches 45 nm in the film annealed by the 10 Hz YAG laser. The sheet resistance of the film generally decreases with the laser frequency in creasing, while the film with the largest grain size obtains the lowest sheet resistance.