Abstract: A "caret" inlet was designed for Mach number 2.0 according to theory of waverider.The experimental investigation on flow characteristics of a large S-shaped diffuser with such an inlet has been carried out.The flow characteristics of the inlet and the S-shaped diffuser have been analysed by means of flow visulization on the walls,measurements of total pressure recovery distribution and velocity vector plots in the sections concerned.The performance of this large S-shaped diffuser was compared with that of the same diffuser but with conventional inlet.It is shown that,under takeoff condition and at the same Ma² of the diffusers,the total pressure recovery of the former is a little higher but the circumferential total pressure distortion index △ σ_o and DC60 of the former are larger than that of the latter.