This paper deepens and develops Galileo's principle of relativity of motion, and summarizes the Laws of relativity and superposition of motion or wave (light). The essence of light is analyzed. Analyze the characteristics of various waves (sound waves, water waves, electromagnetic waves or light waves, etc.) and their relationship with the motion speed of objects (wave sources). Wave acts as a messenger for people to know things, and uses wave (light) as a signal to receive, perceive and know things far away. The observation of an object is an observation perspective effect, not the real motion of the object. The real motion of the wave source can exceed the wave speed, and the observed speed of the object moving at the super wave (light) speed can be much lower than the wave (light) speed in some visual angles, while the observed speed of the object moving below the wave (light) speed will be much higher than the Apollo speed in some visual angles. Objects moving at super wave (light) speed will produce special phenomena when observed from some angles. Superwave velocity (including superlight velocity) of real motion of objects and inversion of observation time sequence are common phenomena. Finally, the superluminal phenomenon of quasars and the technical application prospect of observation angle effect are discussed. This theory is widely used in remote sensing, astronomical observation, microscopic detection, satellite navigation, weather forecast, microscopic observation, medical detection, dynamic identification and so on. All of them are calibrated by the formula of observation angle effect derived in this paper, which can improve the accuracy of observation results. Especially in the observation technology of high-speed moving objects such as high-energy collider, cosmic ray, cosmic radiation and nuclear reaction, the application effect is more remarkable, and more real and accurate results are achieved.