Abstract: The constitution of logical system of physics is expounded. Based on the fundamental thought of Mach＇s logical system of classical dynamics, a rigorous logical system of relativistic dynamics is proposed. The operational definition of mass and force under general case （high or low speed） are given, and the definition of force given by Mach that force is equal to the product of mass by acceleration is criticized and revised. More is discussed, such as experimental verification of Newton＇s second law.

Key words: operational definition, mass, force, dynamics, special relativity