The present application relates to a composition, which comprises: (a) a photopolymerizable substance； (b) a thiol； (c) a photoinitiator； (d) a thermosensitive polymer； and (e) water, and can be used as a bio-ink for preparing a bio-hydrogel for direct-writing 3D printing. The present invention further relates to a method for preparing the composition, and a direct-writing 3D printing method using the composition.
