Disclosed are a robot arm control method, a skin surface treatment apparatus, and a computer-readable memory medium, which relate to the field of mechanical control. the robot arm control method includes steps of: demarcating a to-be-treated surface of an object treated by a robot arm into at least two areas of interest; obtaining, by a three-dimensional scanning device, a three-dimensional point cloud corresponding to each area of interest; optimizing respective three-dimensional point clouds; merging the respective three-dimensional point clouds to obtain an executive point cloud; creating a motion path for the robot arm based on the executive point cloud; and performing, by the robot arm, a treatment to the surface of the object based on the motion path. Compared with conventional technologies, the disclosure has a better cost-effectiveness, an enhanced treatment efficiency, and an improved apparatus safety.