A terahertz frequency tripler using resistive Schottky barrier diodes UMS DBES105a was designed. To enhance power capacity and improve conversion efficiency, an anti-parallel diode pair has been used to realize balanced multiplier structure. The equivalent circuit model of the diode has been built and the component parameters were obtained based on the measured results of S parameters. At terahertz band, the field distribution in circuit is seriously affected by the package of diodes. It means that it is not a good way using the traditional method that directly applying SPICE parameters to the field of terahertz. Therefore the electromagnetic model of diodes has also been built. A 220 GHz frequency tripler was fabricated based on the model of diodes. The maximum output power is 1.7 mW and the minimum conversion loss is 17.5 dB. The conversion loss is less than 22 dB from 223.5 GHz to 237 GHz.