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The purpose of this study is to investigate the experimental equation for the estimation of compressive strength of recycled gravel concrete by non-destructive testing method such as rebound Schmidt hammer and ultrasonic velocity.The main experimental variables were the water-cement ratio, the substitute rate of recycled gravel, the types and amount of admixtures, and the curing time.In comparison with the crushed stone concrete, the recycled gravel concrete shows reduction in rebound number, pulse velocity, static modulus of elasticity and compressive strength. Therefore, the existing foreign equations for the estimate of compressive strength of crushed stone concrete by non-destruction have some difference with the measured data in this study.According to the test results of whole concrete specimens, following equations are suggested.① Rebound hammer method : (r = 0.856)② Ultrasonic pulse velocity method : (r = 0.839)③ Combined method(Rebound & Ultrasonic) : (r = 0.888)