In this study, Hydrologic regime alterations(magnitude, magnitude and duration of annual extreme, frequency and duration of high and low pulse, rate and frequency of water condition changes, Range of Variability Approach) were analyzed by using Indicators of Hydrologic Alterations at the 11 major multi-purpose dam. The analysis result of the magnitude of monthly water conditions during drought season, inflow was $6.38m^3/sec{sim}39.84m^3/sec$ and outflow was $20.36m^3/sec{sim}49.43m^3/sec$, was increased $1.84%{sim}200.98%$. The analysis result of the magnitude of monthly water conditions during flood season, inflow was from $79.06m^3/sec{sim}137.12m^3/sec$ and outflow was from $65.32m^3/sec{sim}80.16m^3/sec$, was decreased from $18.19%{sim}40.39%$. The analysis result of the magnitude and duration of annual extreme, 1-day minimum was increased $82.86%{sim}2,950%$, but 1-day maximum was decreased $34.78%{sim}83.96%$. The analysis result of the frequency and duration of high and low pulse, low pulse count was decreased $29.67%{sim}99.07%$ and high pulse count was also decreased $4.6%{sim}92.35%$ after dam operation. Hydrograph rise rate was decreased $15.84%{sim}79.31%$ and fall rate was $1.97%{sim}107.10%$. RVA of 1-day minimum was increased $0.60{sim}2.67$, also RVA of 1-day maximum was decreased $0.50{sim}1.00$.