Blades of turbomachine are important components to produce power like turbines or pressure compressors working in a complicated condition with high pressure, high temperature and three dimensional air flows as well. The aeroelastic problem like flutter may occur during different working states. Flow-induced vibration of the blade with the coupling of bending and torsion is investigated to reveal the mechanism of flutters. Averaging method and power flow approach are used to demonstrate the flutter behaviours of interaction between an isolated blade and the quasi-steady flow. The relation between amplitudes and the frequency of blades vibration is given to predict flutters, which is beneficial to aeroelastic designs of the turbomachine.