A novel sensor based on the Differential Group Delay（DGD） of FBG was proposed in this paper. The evolution of the DGD with respect to pressure was studied theoretically and experimentally. A theoretical model for pressure sensing by use of DGD was built and numerically simulation was also carried out. The experimental pressure sensitivity was 424.2 ps/MPa at 0 MPa to 0.3 MPa. Good agreements between experiment results and numerical simulations could verify the feasibility of the method.