In this paper, we aim to find a control parameter in two-dimensional parabolic equations with the over-specification conditions. The present method is implemented on two problems with different over-specification conditions. This method produces new polynomials by com-bining Chebyshev polynomials and using an unknown parameter. The numerical solution of the problem is estimated by the linear combination of the new polynomials. By collocation method, the unknown coefficients of this linear combination and new unknown parameter are obtained by solving a nonlinear system by the least-squares method at each of the colloca-tion points. Finally, with interpolation on all functions obtained at all collocation points, we will give an approximation solution. The results of this method are calculated for two types of interpolation points. The results obtained from the present method are better than the results of finite difference method.