Abstarct: Concrete as a very important building material has been used in the construction industry and other structures for many years. If this material is constructed and maintained in accordance with the proper principles it would have high reliability and durability. The first step in any repair or improvement project, is reasonable and accurate assessment of the current state of the structure. But because of the choice of inappropriate materials, poor quality and lack of maintenance run, particularly in the hard and corrosive areas failures occur for concrete. Concrete may also declines and damages during application and as a result, the existing concrete may not be as originally intended and designed to operate. In many years, for increasing property of cement and concrete material, the different physical and development experiments done. During of different research, many method such as micro silica, image analysis, furnace slag and …, have been for increasing quality of concrete. The quality of concrete and cement has been depended of physical, chemical and mineral properties. In baxse of this properties, researchers use of suitable instructions for improving performance of cement and concrete. determination hole and porosities of concrete is necessary to retrofitting cement and concrete mixture. In previous research, flash laser method was used to measurement special heat. In order to improve on this research and increasing quality of concrete, the holes of concrete checked. In this study, considering the durability of concrete, locate the air hole in concrete using Compton scattering of gamma rays in the Monte Carlo method has been used to exploit those involved in concrete. Materials used in this experiment, cubic concrete is made of cement with dimensions 15 cm. HPGe detector on one side of the concrete and fountain 137Cs were on the other side of concrete. The results of positioning holes, obtained by the simulation code and the air hole depth and spatial resolution both holes Were examined And contrast results obtained. And in this case, the maximum depth of the air cavity can be etermined. According to the study A hole in the concrete surface absorbs Most of the attenuation coefficient and energy and Causes increasing concrete demolition and . The entrance of the detector collimator between different rods such 1.5, 1, 0.5, 0.25 cm for entrance collimator was determined and The radius of the crater with the highest contrast and high-resolution 1 cm were found . the relative error of Contrast was below 5%.