The computation with the theory of modified Brayton Cycle indicates that higher cooling power and coefficient of performance for a pulse tube refrigerator can be achieved with He-H_2 mixture as working gas than those with pure He in the temperature region of 30 K. In addition, it is found that Er_3Ni, a regenerative material, is able to absorb H_2 and produces Er_3NiH_x. The computation presents that the regenerative performance of Er_3NiH_x is better than that of Er_3Ni due to its higher volume specific heat. Experimental results show that the pulse tube refrigeration performance in 30 K temperature region is enhanced greatly with He-H_2 mixture and Er_3NiH_x packing. The computation with the theory of modified Brayton Cycle indicates that higher cooling power and coefficient of performance for a pulse tube refrigerator can be achieved with He-H 2 mixture as working gas than those with pure He in the temperature region of 30 K. In addition, it is found that Er_3Ni, a regenerative material, is able to absorb H_2 and produces Er_3NiH_x. The computation presents that the regenerative performance of Er_3NiH_x is better than that of Er_3Ni due to its higher volume specific heat. Experimental results show that the pulse tube refrigeration performance in 30 K temperature region is enhanced greatly with He-H 2 mixture and Er_3NiH_x packing.