Pursuing a more efficient signal amplification strategy is highly demanded for improving the performance of the promising cathodic photoelectrochemical (PEC) sensors. In this work, we present an extremely effective dual signal amplification strategy by the integration of a Z-scheme nanohybrids-based photocathode with the effective signal modulation of an organic photoelectrochemical transistor (OPECT) device. Specifically, photocathodic gate material of CdTe-BiOBr nanohybrids with a Z-scheme electron-transfer route was designed and synthesized for preliminary improvement of the activity of the photogate; afterward, signal modulation of the OPECT system by the photocathodic gate of CdTe-BiOBr was then accomplished for further signal amplification by 2 orders of magnitude. As a result, the output PEC signal of CdTe-BiOBr was enhanced by 17.5-fold as compared to BiOBr, and the channel current (IDS) of the OPECT device was 117-fold magnified than its gate current (IG) response. Exemplified by tetracycline (TC) as a model target and aptamer as the specific recognition element, a versatile cathodic aptasensing platform was constructed based on the proposed OPECT device. The introduced OPECT aptasensor merits advantages, including a good linear range (1.0 × 10-12 to 1.0 × 10-6 M), a low limit of detection (4.2 × 10-13 M), and superior sensitivity than the traditional PEC methods for TC detection, which represents a universal protocol for developing the innovative photocathodic OPECT sensing platform toward accurate analysis.