To acquaint the testing errors of nonlinear dynamic shear modulus ratio and damping ratio using the prevailing resonant column technique, two typically representative test groups, i.e., a general group and a professional group, are designated. The error distribution and the relevant statistic characteristics of dynamic shear modulus ratios and damping ratios of sand are systematically studied on a single resonant column apparatus. The testing results indicate: (1) the test data of nonlinear dynamic shear modulus ratio and damping ratio of the two groups are normally distributed at different characteristic shear strains, and the variability indices are closely consistent for the two groups; (2) the mean values of the two groups are similar while the confidence interval of the general group is particularly larger than that of the prefessional group with a coefficient of variance 5 times larger than that of the professional group; (3) the coefficient of variance of shear modulus ratio is remarkably smaller than that of damping ratio. On the current testing technique of resonant column apparatus, the test accuracy of shear modulus ratio and damping ratio on sandy samples by an experienced individual can be quite satisfactory but on the other cases the testing error cannot be neglected that parallel tests should be performed and the testing skill of the operators should be improved.