Abstract: A method and an apparatus for liquid safety-detection with a radiation source relate to a radiation detecting technology field. The main steps of the method of the invention are: an article to be detected being conveyed into an operation zone within a radiation shield field; the ray emitted from a radiation source passing through the article to be detected, and being received by a detector; the detector transmitting the received ray signal to a data collector; the data collector amplifying and forming the ray signal, and transmitting such data and the data collected by thickness measuring probing heads to a data processing computer; and the data processing computer processing the two groups of data to derive the density and atomic number of the detected liquid, comparing the result with the densities and atomic numbers of dangerous articles in a existing database, and displaying the detected information of the detected article.