Railroad ballast materials tend to degrade due to the increase of ballast abrasion and fracture that results in decreasing the capability of shock absorption, interlocking friction, and the resistance to track irregularity. Therefore, it is necessary to establish a methodology to improve or maintain the structural condition of ballast materials which is in the middle of fouling. This study aimed to investigate the effect of reinforcement on the fouled ballast using ballast stabilizer. Field experimental program was conducted to compare the lateral ballast resistance in case of before and after application of ballast stabilizer. A series of laboratory repetitive load triaxial compression test was then performed to compare the accumulated plastic strain in case of before and after application of ballast stabilizer to the ballast materials having a different level of Fouling Index(FI). In the event of application of ballast stabilizer, the accumulated plastic strain decreased by 41.8 and 28.8 percent, respectively, when the FI was 14 and 21, which appears to indicate the ballast stabilizer is effective for the moderate level fouled ballast materials.