Inertia force is one of the most basic conception in physics, and is also an very important idea at the early period when we learn this class. This ordinary and simple idea, at one time or another, arose many consideration and anatomization by physicists. Prologue begins with the ideas about force and inertia, this article put comprehensive consideration on the reason why the argue about inertia holds so long. The dynamic problem in both inertial coordinate system and non-inertial cordinate system is discussed audaciously. Basede on relative theory, a few viewpoints views on both inertial coordinate system and non-inertial cordinate system are presented.