Heterojunction devices based on two-dimensional materials have been widely studied in the fields of electronics and optoelectronics. As the complexity of the chip system increases, the ability to realize multi-function in a single device is increasingly in demand. Here, we propose a multifunctional device based on graphene/silicon heterojunction, which can operate in photodetection mode or tunable rectifier mode. The heterojunction barrier is tunable by the external electric field. The photodetection range covers ultraviolet to visible, and the responsivity can reach 51 A/W and 495 A/W at 266 nm and 532 nm while keeping the off-state current at a low level of 10 −8 A. With the control of the external electric field, the device can also function as a tunable rectifier to achieve three states: positive-pass, off, and negative-pass, which can be applied in signal processing and logic circuit. The multifunctional integrated device has potential in future optoelectronic logic applications while reducing the cost and the device footprint.