The invention belongs to the technical field of building testing, and relates to an automatic controllable testing sand sample preparation device and method. The method includes the steps: firstly, connecting a deceleration strip brake motor with a frequency converter and then connecting the deceleration strip brake motor with a computer and an operation plc (programmable logic controller); secondly, inputting the movement track and the movement speed of a horizontal rail to the operation plc and checking whether a horizontal displacement system normally works or not; thirdly, assembling a vertical displacement control system and the horizontal displacement system, connecting the systems to the computer and the operation plc and checking running before testing sand sample preparation; fourthly, determining the drop distance and the flow of sand shakeout and the movement track and the movement speed of a sand unloading system, controlling a micro-motor to perform sand shakeout by the operation plc, repeating the sand shakeout process until geo-technical testing sand sample preparation is finished, detaching the sand unloading system and finishing testing sand sample preparation. Automation degree is high, the sand sample preparation process is safe, soil preparation time is short, and reliable guarantee is provided for rapid geo-technical testing.