  Within the framework of a model universe with time variable space dimension
(TVSD) model, known as decrumpling or TVSD model, we study the time variation
of the gravitational coupling constant. Using observational bounds on the
present time variation of the gravitational Newton's constant in
three-dimensional space we are able to obtain a constraint on the time
variation of the gravitational coupling constant. As a result, the absolute
value of the time variation of the gravitational coupling constant must be less
than $\sim 10^{-11} {\rm yr}^{-1}$.
