The failure assessment for the defects in multiple corroded region has been considered with the real-size pipeline burst tests and the associated Finite Element Method. The corroded gas pipeline made of X65 steel with various types of artificially machined pits has been used for a number of series of burst tests on gas pipeline. The failure pressures for the designed multiple corroded defect on gas pipelines have been measured by using in-situ burst testing and classified with respect to each designed defect sizes - length, width and depth - and distance between defects. The result from the experiments has been modeled and compared with Finite Element Method. As the result of FEM simulation, the failure pressure in multiple defects is lower than that in single defect, and closer to failure pressure in single defect of total length of defects in multiple defects as the distance between each defect is closer.