AbstractA high specific pumping cryopump system is designed for the neutral beam injector of the Large Helical Device (LHD NBI). The cryopump consists of several module panels that have the radiation shield of louver blind baffle structure. Two types of the louver blind baffle are designed, and both show the particle transparent efficiency over 50% according to the Monte Carlo simulation. This prediction was confirmed by test on the small model cryopump. The engineering models of these pumps, with a pumping speed of 450 m3/s each, are now under construction for the test stand of LHD NBI.