Abstract: An organic photoelectrochemical transistor (OPECT) sensing system has been constructed for the detection of cardiac troponin I (cTnI) protein by fabricating a tungsten oxide/hydrogen-bonded organic framework (WO₃/HOF) gate electrode with excellent photosensitive signals. The carboxyl group in HOF reacted and binded with the amino group in the trigger DNA strand. The aptamer strand carrying the signal bursting agent polydopamine （PDA） was introduced into the electrode by complementary pairing with the trigger DNA strand. In the presence of the cTnI protein, due to the specific recognition with the aptamer, the PDA was released from the electrode and the channel current was enhanced. After the effects of HOF concentration, PDA concentration and aptamer binding time on the OPECT sensing system were investigated, and the optimal experimental conditions were established. The final experimental results showed that the cTnI proteins had a good linearity from 1 pg/mL to 100 ng/mL, with a detection limit of 280 fg/mL.