In this paper, a graphene composite structure based optical absorption pressure sensor is proposed. First, a composite structure which is composed of PDMS micro-pyramid structure, graphene film, and waveguide is introduced. The sensitive mechanism and dynamic working state of the pressure sensor are analyzed continuously. Second, the mapping between the pressure on PDMS and its contact area with the graphene film is deeply analyzed, as well as the optical transmission properties of graphene combined with waveguides, followed by a series of simulations about the optical power output performance facing different pressure conditions. Finally, the designed sensor samples are prepared and a series of performance verification experiments were carried out. The experimental results show that the range of the pressure sensor is 0-870kPa. The sensitivity in the pressure range of 0-100kPa is 2.83×10-1µW/kPa. The experimental results effectively prove that the designed graphene composite structure based optical absorption pressure sensor has high sensitivity and good repeatability, which further verifies the feasibility of the design and analysis method.