In this study

the count rate ratio of

228

Ac was obtained from a standard sample of

232

Th.The ratio is not interfered by the overlap peak

which is ascribed to absence of

40

K in the standard sample of

232

Th.Using this ratio

instead of overlap peak separation

the

40

K interference can be eliminated.The method based on the ratio is reliable because gamma-ray emission probability of

228

Ac varied in different databases is not required.No system error is presented in this method.The radioactivity of

40

K in a uranium ore sample is measured by this method through HPGeγspectrometry.