In　this　paper,　the　equivalent　circuit　model　of　UTCHPT　is　established　to　simplify　the　microwave　optical　amplifier　and　mixer　design.　Based　on　the　equivalent　circuit　model　of　HBTs,　the　photo-generated　current　in　UTC-HPT　is　introduced　reasonably　as　part　of　base　current.　The　influence　of　photo-generated　carriers　on　several　equivalent　circuit　components　such　as　trans-conductance,　barrier　capacitor,　diffusion　capacitor　and　junction　resistor　are　considered　carefully　in　the　model.　Finally,　the　collector　output　current　is　checked　to　verify　the　model　validity　and　the　photo-current　gain　and　the　photo-characteristic　frequency　are　analyzed　with　the　established　model.