This paper deals with a numerical study of mixed convection flow and heat transfer inside lid-driven cavity. The main purpose in this present study is to maximize the heat transfer. For that, a new lid-driven cavity with two wavy walls and non-uniform heating on both sidewalls has been proposed. The two horizontal walls are considered isolated, while two variable sinusoidal temperature distributions are imposed to the left and right vertical side walls with different amplitudes and phases. A finite volume method is used to solve numerically the non-dimensional governing equations. The tests were carried out for Richardson numbers which vary from 0.01 to 100, amplitude ratios from 0 to 1, and phase deviations from 0 to , meanwhile the Prandtl number is fixed to Pr = 0.71. The distributions of streamlines, isotherms, and the variations of local and average Nusselt numbers with the variation of Richardson numbers, amplitude ratios and phase deviations are presented and compared with results given in the literature. The comparisons have showed a satisfactory agreement. Furthermore, the present study showed that the wavy walls with variable temperature have strong influence on enhancing heat transfer.