A topology structure of operational transconductance amplifier is proposed to be devised in this paper. In order to make it have the feature of high-speed, large bandwidth, and high stability, a two-stage cascode structure amplifier is designed by using cascaded single-stage amplifier. And several important parameters are calculated and analyzed theoretically. Finally the designed cascode two-stage amplifier is debugged by using Hspice. And the related parameter values are obtained. The magnification is more than 100dB, unity gain bandwidth is about 635MHz, and output swing is 4V. And the total transconductance of operational transconductance amplifier is 8.8A / V.