In this paper, the theory of atomic cooling in an integrating sphere is studied. During designing an integrating sphere system, the effects of the parameters of the sphere on the cooling, including the reflectivity of the material, the shape of the sphere and holes in the sphere have been considered carefully. The experiment of 87Rb atomic cooling in an integrating sphere was performed. The experimental results show that the atoms in the integrating sphere are cooled down evidently. And the relation between the detuning of the cooling laser and the absorption signal of cold atoms was measured.