Carbon fiber reinforced plastic (CFRP) composites have superior properties, including high strength-To-weight ratio, high modulus-To-weight ratio, high fatigue resistance, etc. These properties make CFRP composites being popular in many kinds of industries. Due to the inhomogeneous and anisotropic properties, and high abrasiveness of the reinforcement in CFRP composites, they are classified as difficult-To-cut materials in surface grinding processes. Many problems (including high cutting force and low machining efficiency) are generated in conventional surface grinding processes. In order to reduce and eliminate these problems, rotary ultrasonic machining (RUM) surface grinding of CFRP composites is conducted in this investigation. Effects of ultrasonic power in different machining levels are of great importance in RUM surface grinding processes. However, no investigations on effects of ultrasonic power in different machining levels are conducted in such a process. This investigation, for the first time, tests the effects of ultrasonic power on output variables, including cutting force, torque, and surface roughness in different machining levels. This paper will provide guides for future research on effects of ultrasonic power in different combinations of machining variables on output variables.