This work presents a 2.5GHz 90nm CMOS triple gain mode LNA for WiMAX standard. Because of the high linearity and wide dynamic range requirement in WiMAX applications, the LNA provides triple gain mode for different receiving conditions. The LNA allows to be switched among high gain mode, IMD sinking mode, and high linear mode. Without introducing additional inductors in three gain modes, this work is suitable for system integration. The simulation result shows 1.8 dB noise figure can be achieved at high gain mode for small input signal levels. With IMD sinking technique, the input-referred IP3 is about 7.5 dBm for large interferences. For larger input signal levels, the input P1dB at high linear mode is -2.3 dBm.