Described herein is a composition for submucosal injection comprises a biocompatible modified starch and a pharmaceutically acceptable carrier for injection. The biocompatible modified starch is in an amount ranging from 0.2 wt % to 50 wt % of the total weight of composition. The biocompatible modified starch is selected from one or more of the group consisting of: etherified starches, esterified starches, cross-linked starches, pre-gelatinized starches, graft starches and composite modified starches, which has a molecular weight ranging from 3,000 to 2,000,000 daltons, a water absorbency capability of at least twice of its own weight, and a particle size from 500 nm to 1000 μm. The viscosity of the composition ranges from 9 mPa·s to 150,000 mPa·s at 25° C. The present disclosure also provides a combination reagent for submucosal injection, comprising the above-mentioned biocompatible modified starch and the pharmaceutically acceptable carrier for injection.
