The concept of the variable circular gear is introduced.The full constructive process of its teeth profile is given with the derivation function（DF） methods.It is provided that the variable circular profile satisfies the requirement for uniform motion.The equations of its teeth profile and others are derived.Some Characteristics of the teeth profile is discussed

and the example of a variable circular gear pair is given.Since the load capacity is high and specially it can be manufactured precisely with the NC technology

variable circular gear will be used in some high-load application.