This calculation allows obtaining approximation of 3D data using generalized Pade (rational) functions. Coefficients of these functions are derived from the Least Residual Sum of Squares (RSS) condition. Traditional form of RSS leads to a system of nonlinear equations in the case of rational functions and therefore it is rather costly. The new form of RSS which leads to linear equations was suggested for 2D regression analysis in paper 'On regression analysis with Pade approximants' (August, 2022, DOI: 10.48550/arXiv.2208.09945) by G.Yevkin and O.Yevkin. In this calculation we have expanded this approach to the case of 3D regression analysis.