Past studies show that soil liquefaction due to a long duration earthquake with low acceleration, for example as observed in the Tokyo Bay area in the 2011 Great East Japan Earthquake, is largely affected by liquefaction strength for a large number of loading cycles. It is, therefore, extremely important to know the liquefaction resistance for a large number of loading cycles. This paper describes the results of the hollow cylindrical cyclic torsion shear tests that were conducted to ascertain the effects of grain size distributions on liquefaction resistance for a large number of loading cycles. The test results clearly show that the tendency of a decrease in liquefaction resistance for a large number of loading cycles is influenced by mean grain size, inclination of grain size distribution, and so on. Finally, the effect of liquefaction resistance curve characteristics on the assessment of liquefaction potential is examined using the cumulative damage theory.