Although Support Vector Machines(SVM) succeed in classifying several image databases using image descriptors proposed in the literature, no single descriptor can be optimal for general object categorization. This paper describes a novel framework to learn the optimal combination of kernels corresponding to multiple image descriptors before SVM training, leading to solve a quadratic programming problem efficiently. Our framework takes into account the variation of kernel matrix and imbalanced dataset, which are common in real world image categorization tasks. Experimental results on Graz-01 and Caltech-101 image databases show the effectiveness and robustness of our algorithm.