A 3D ultrasound imaging device including an ultrasound probe assembly and echo analyzer. The ultrasound probe assembly includes a housing and an acoustic window abutted against the housing to form a sealed chamber, wherein the surface of the acoustic window contacts with the breast of the human body to be examined an ultrasound transducer moves at a first speed back and forth within the sealed chamber and performs high-speed pre-scanning through the acoustic window to obtain initial ultrasound signals the echo analyzer analyzes the initial ultrasound signals to determine a quality of a ultrasound image acquired by the high speed pre-scanning and the ultrasound transducer then moves at a second speed to perform another scan to acquire new ultrasound signals. A 3D ultrasound imaging method is also disclosed.
