The present invention provides a non-radical photo-crosslinked hydrogel preparation method, comprising the following steps: a component A is dissolved in a biocompatible medium to obtain a solution A, component B-hydrazide, hydroxylamine or primary amine high molecular derivative is dissolved in a biocompatible medium to obtain a solution B; the solution A and the solution B are evenly mixed to obtain a hydrogel precursor solution; under illumination, aldehyde group produced by light excitation of o-nitrobenzyl in the component A of the hydrogel precursor solution is crosslinked with hydrazone, hydroxylamine or primary amine group in the component B in the form of respective formation of oxime and Schiff base to produce the hydrogel. The present invention also provides a kit for the hydrogel preparation, and application of the hydrogel in tissue repair, beauty and as a cell, protein or drug carrier. The tissue surface light-situ gel can be achieved by the hydrogel, in particular, wound surface in-situ thin glue formation can be achieved, and the hydrogel is especially suitable for clinical wound surface tissue repair and isolation.