A method of intracranial ultrasound imaging applied in detecting a cranial blood vessel having blood filled with micro-bubbles formed by an injected contrast agent and generating blood vessel images includes: (1) emitting a plurality of ultrasound signals having bandwidths to the cranial blood vessel in sequence, (2) receiving an echoed signal from a micro-bubble, (3) performing a spectral analysis on the echoed signal and extracting a low-frequency response, the bandwidth of the low-frequency response similar to the bandwidth of the ultrasound signal, and (4) calculating a location and a depth of the micro-bubble in the cranium according to the low-frequency response and generating a corresponding blood vessel image.