Abstract: The velocity of light in vacuum has both the kinematical character and dynamical character as a prediction of the Maxwell＇ s theory. The principle of constancy of light velocity in the special relativity provides not only the Lorentz space-time transformation and some kinematical effects such as the shrink ruler effect, but also the non -trivial constraints on the dynamics structure of the theory. We devise several typical paradoxes and analyze them in detail to explain how the kinematics constrain the dynamics in the special relativity. Specifically, the dynamical theory of interaction, which can be harmonious to the relativistic kinematics, must be a field theory with a limited velocity of propagation of interactions, which is exactly the velocity of light in vacuum, and the transformation of the fields should be determined by the Lorentz space-time transformation. Further analysis makes clear that the field should have momentum, which is usual character of matter.

Key words: principle of constancy of light velocity, shrink ruler effect, transverse force, field momentum