In this study, 838 ground motion records from the 1999 Chi-Chi earthquake in Taiwan are used to compute the amplification factors between average spectral acceleration (velocity, displacement) in acceleration (velocity, displacement) sensitive region and peak ground acceleration (velocity, displacement). The results are compared with those presented in literatures. This study also examines the impact of site condition (VS30), closest site-to-source distance and hanging/foot-wall effect on amplification factors. The study shows that (1) among the amplification factors for spectral acceleration, velocity and displacement, those for spectral velocity have highest dependency on VS30 and distance; (2) amplification factors for spectral acceleration and velocity are similar to those proposed by Newmark and Hall in 1982s, and those for displacement are higher than the factors developed in other studies.