To analyze the effect of wear of wheel profile on the running stability of rolling-stock, theoretical and experimental studies were conducted on the profiles used in conventional lines. In experiment using 1/5 scale model to verify the results of the theoretical analysis, the test results of the critical speed for worn wheel profile samples show similar trend. In case of the conical type wheel profile(Profile 40), the equivalent conicity is increased with flange wear. But in case of the arc type wheel profile(Profile 20h), the equivalent conicity is decreased with flange wear. And the critical speed of the bogie was inverse proportion to the equivalent conicity. It is shown that the variation of the critical speed with the wheel wear could be changed according to the design concept and wear pattern of wheel profile. Results of the theoretical and experimental studies are discussed here.