A method and an apparatus for liquid safety-detection with a radiation source relate to a radiation detecting technology. The main steps of the method of the invention are: conveying an article to be detected into an operation zone within a radiation shield; allowing a ray beam to be emitted from the radiation source, to pass through the article to be detected, and to be received by a detector; transmitting the received ray signal to a data collector by the detector; amplifying and forming the ray signal, and transmitting such data to a data processing computer by the data collector, and transmitting a data collected by thickness measuring probing heads to the data processing computer by the same; and processing a data from the data collector and a data from the thickness measuring probing heads to derive the density and atomic number of the detected liquid, comparing a result with the densities and atomic numbers of dangerous articles in a existing database, and displaying the detected information of the detected article, by the data processing computer. Comparing to the prior art, the invention is not subjected to the affection of the outside package of an article and has great anti-interference, and has the features of small volume, high accuracy of detection, easy shielding, and high use safety and reliability.