The centre of earth is equator and if equator is the centre of earth and as we know the gravity is maximum at centre of the earth then why the gravity is less there?
(Evidently, the question is posted out of some misconception or confusion)
Centre of earth means the centre INSIDE THE EARTH, and there the value of g is zero.
At the equator, the distance from the centre is maximum and therefore g is the minimum. Further, the effect of rotation is maximum at the equator as the distance of any particle on the surface is farthest from the axis of rotation at the equator and any object at the equator requires maximum centripetal force which is derived from the gravitational force of earth. Thus in both ways, g is minimum at the equator.