Abstract: Traditional Power Minimization problem need complicated calculation and is not applied in practice very well.To overcome this problem,formulas are transformed and solved,and the solution of Water-Filling can be applied,take advantage of properties of Water-Filling,agilely adjusting Water-Level instead of processing complex Water-Level searching process.Based on Water-Filling algorithm,fast power and bit allocation algorithms in Power Minimization for multi-channel wireless communications are realized.Simulation results shows,compared with existing algorithms,proposed algorithms runs multiple times faster.