The decay parameter at the high frequency (kappa value, ) introduced by Anderson and Hough (1984) is measured from 54 stations situated in and around the Taipei basin, northern Taiwan. Different frequency windows for the S‐wave amplitude spectra are used to measure the value for each individual record. The preferred values are determined by the least‐squared fitting with the best correlation coefficient. The site‐specific values, which are computed by removing the anelastic effect of regional geological structure by grouping into the crustal and subduction events according to the focal depth and site classification (i.e., class B, C, D, and E sites), are calculated to be in the range of 0.034–0.066 s. We correlate the values with the averaged shear‐wave velocity of the topmost 30‐m layer and find the independence of on . In addition, 28 stations lie on sediment in the Taipei basin. The gradient of versus the sedimentary thickness to the Tertiary base in the basin is calculated, and then used to estimate the effective quality factor of the layer. is 75.3 for the whole sedimentary layers (above the Tertiary base). Given one standard deviation, are in the 41.9–376.7 range. can provide an accurate referred parameter for the future ground‐motion simulation applications.