We report on the static and dynamic characteristics of optically modulated resonant tunneling diode oscillator (RTDO) formed in double-barrier quantum-well structure. Under the illumination of Ti:Sapphire laser, the dc current-voltage (I-V) curves of RTDO shifted towared lower voltages. This characteristic was found to odify the series resistance, negtive differential resistance, capacitance, and the inductance of the RTDO. As a result, the resonant frequency of TRDO centered at 5.302 GHz was found to decrease about 20 MHz under the laser illumination. At a constnat bias voltage, the oscillation frequency decreased linearly as the laser power was increased.