Radiation detection method has been developed through years. It started from the complex module tools to simple handheld instrument. Recently, the more ease method has been developed with the help of smartphone application. To detect radiation using smartphone usually required the external tools connected to the phone as detector, but there is one application that did not. This application only required complementary metal-oxide semiconductor (CMOS) part of camera. The application is a game changer in radiation protection because nowadays smartphone is in everyone’s pocket. The application needs to be tested to ensure its effectiveness to detect radiation. The application has been tested by the previous research and it is effective to detect radiation. In this research, CMOS will be tested to detect radiation leakage of x-ray tube. The aim of this research is to find the effectiveness of CMOS in smartphone for radiation leakage detection of x-ray tube. The finding will help the radiation worker detect leakage radiation of x-ray tube using smartphone in case of the absences of surveymeter in the facility. The radiation from x-ray machine were detected and measured three times by Iphone 6s, Xs, and 11 using RadioactivityCounter. To ensure there was a leakage, surveymeter is used as a comparative modul. The data obtained from the experiment was analyzed using t-test. The result show that percentage error of Iphone 6s, Xs, and 11 Consecutively were 93.4%, 98.2%, and 98.9%. which mean CMOS in these said phone could detect and measured radiation ineffectively. This due to the low leaked intensity x-ray that came from x-ray machine. From the T-test anaysis found that only Iphone 11 had linear comparison to surveymeter