A rubidium double magneto-optical trap(MOT) system for Bose-Einstein condensation experiments has been set up. A slow atomic beam has been obtained with a low-velocity intense source (LVIS) and used to transfer atoms into an ultra-high-vacuum (UHV) MOT. By maintaining a pressure difference of 3 orders between LVIS-MOT and UHV-MOT, a lowest pressure of 1×10-9Pa can be achieved in UHV-MOT. The flux of the slow atomic beam is 1×109/s. About 4×108 87Rb atoms can be loaded into UHV-MOT. In this paper, maximum number of atoms captured in MOTs under two typical conditions have also been discussed.