As a significant p-type semiconductor, NiO is widely studied for its gas sensing and electrochromism characteristics, whereas researches concerning its photodetection properties are rarely reported. Herein, we fabricated a photodetector based on NiO/Bi₂Te₃ heterostructure and studied the influence of NiO’s concentrations as well as the Localized Surface Plasmon Resonance (LSPR) effect of the Au NPs on the device’s photoresponse.For the device fabrication, NiO film was spin-coated on the FTO glass, followed by baking and annealing to form high quality crystal film. Then, Chemical Vapor Deposition (CVD) method was adopted to lay Bi₂Te₃ nanoplates on the NiO film, forming the NiO-Bi₂Te₃ heterostructure. Finally, the device was achieved via photolithographic process and Ag electrodes deposition, featuring a vertical structure with FTO working as the anode and Ag serving as the cathode.X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) results demonstrate the favorable crystal quality of NiO film and Bi₂Te₃ nanoplates. Energy Dispersive Spectrometer (EDS) image manifests the uniform distribution of different elements and Photoluminescence (PL) spectra were applied to study the mechanism of electron-hole separation. All these results could be condensed to the point that the NiO film with the concentration of 0.5 mol/L shows the optimal crystal quality and the doping of Au NPs aids the separation of electron-hole pairs. Furthermore, we also performed photo-electric tests to evaluate the influence of the NiO concentration and the results show that the device achieves optimal response with the concentration of NiO fixed at 0.5 mol/L, which meshes well with the characterizing results.In addition, tests regarding photoresponse to wavelength, power density and on/off switching were conducted in ambient environment. With the presence of Au NPs, the maximum responsivity (R) of the device reaches 1236 mA/W, about 21% higher compared to that of the pristine NiO, owing to the boosted light absorption caused by the LSPR effect of Au NPs. To elucidate the weak signal detecting ability, the specific detectivity (D^*) of the device is calculated and it attains the value of 5.97×10¹⁰ Jones. Besides, the photo gain exceeds 400%, indicating that there are more than 4 photoexcited carriers generated by per absorbed photon. Beyond that, the formation of Schottky contact between NiO and Au NPs will facilitate the separation of electron-hole pairs, thus accelerating the response process and shrinking the rise time (T_r) and decay time (T_d) to 92 ms and 62 ms, respectively. The study corroborates the enhancement of photoresponse resulted from the two internal electrical field due to the introduction of NiO/Bi₂Te₃ junction and Au/NiO Schottky junction as well as the LSPR effect from Au NPs.This research offers a feasible approach for the realization of NiO-based photodetector and sheds light on the enormous potential of the NiO's application in photodetection.