In this study, the modified cyclic triaxial tests with Joomunjin standard sand are performed for dynamic deformation characteristics, such as Young`s moduli and damping ratio. The cyclic triaxial test is equipped with Local Displacement Transducer (LDT) on the outside of a cell which has a range from to of shear strains, (%), instead of conventional cyclic triaxial test which has linear variable displacement transducer (LVDT) with low precision. With the small strain control, tests were carried out at various loading rates, void ratios, and effective confining pressures. Based on the test results, such as dynamic deformation characteristics, shear modulus, and damping ratio, it is found that the test can measure more range of medium strains (0.02-0.2%) than results obtained from conventional test (resonant column test). For the medium strain range, dynamic deformation characteristics investigated by the cyclic triaxial test are also different from those predicted by nonlinear model in conventional test.