Abstract: Through centrifugal model tests,the influence of plate size on the results of plate loading tests was studied.It was shown that the difference of the ultimate bearing capacity between f 56 cm and 80 cm plate was up to 27% to 40%.For the loose ground(relative density 34%),the scale effects could be neglected,but for the dense ground(relative density 78%),the scale effects would influence the results of plate loading tests in the rang of plate size suggested by Specification for Foundation Design of Construction Ground(GB50007-2002)(56 cm to 80 cm).Even for the plate with diameter 80 cm,the bearing capacity factor obtained from the tests was 1.2 times of that excluded the scale effects.According to the centrifugal test results,the corrected formulas of scale effect and plate size were introduced and the results of plate loading tests were modified.