A new approach is introduced to enhance supercontinuum (SC) spectrum in a dispersion-flattened/decreasing fibre with a convex dispersion profile. A flat SC spectrum nearly extending from 1200nm to 2100nm can be generated based on this scheme. It is found that group-velocity dispersions (GVD) and self-phase modulation (SPM) effects are the primary factors for pump pulse compression and SC spectrum generation, stimulated Raman scattering (SRS) effect plays an essential role on the final SC-spectrum bandwidth and flatness, but self-steepening effect can be ignored.