We demonstrate a tunable long wavelength photodetector which is fabricated by bonding a GaAs-based filter with a InP-based p-i-n detector. Through thermo-tuning, the peak wavelength red shifts from 1 540.1 nm to 1 550.6 nm under a bias voltage of 13 V,a tuning range of ]0.5 nm is realized with the linewidth maintaining 0,6 nm and the quantum efficiency of the device keeping around gg %. The tuning theory is analysed, and using the transmission matrix method ,we simulate the transmission spectrum of the filter. The experimental results show that they are validated.