Several technologies such as radiography are available for monitoring inside the pipelines. The nondestructive testing (NDT) method is one of the attractive techniques for corrosion detection inside the pipelines. Sometimes, corrosion detection in the pipelines is quite difficult due to lack of access to the outer part. Therefore, backscatter radiography as an NDT inspection technique for in situ detection of corrosion inside the metallic pipelines should be conducted. The Monte Carlo calculation-based simulation was applied to propose a practical design for corrosion detection inside the pipelines without access to back of them. The results showed that the model can detect corrosion location inside a pipe with acceptable accuracy.