The invention discloses an amphiphilic ternary polymer brush and a nano capsule. The amphiphilic ternary polymer brush has the following general formula, wherein A is polymer main chain, B is lipophilic polymer side chain, C is photo-crosslinked polymer side chain, D is hydrophilic polymer side chain, and the side chains B, C and D are randomly grafted onto the main chain A; and the nano capsule is prepared through dispersing the amphiphilic ternary polymer brush into an oil-water two-phase system, and then performing light crosslinking reaction or reaction initiated by light. The amphiphilic ternary polymer brush solves the difficulty that the particle size of the capsule can not be adjusted and controlled effectively by using the conventional segmented copolymers, and the size of the prepared photo-crosslinked nano capsule is easily adjusted and controlled; the nano capsule prepared by the emulsion self-assembly method is simple in operation and easy to use in large-scale preparation; the prepared hollow nano capsule is large in casting quantity; the photo-crosslinked nano capsule provided by the invention is stable, and according to the light crosslinking method, nontoxicity and safety are reliazed, and the environmental protection is realized. The amphiphilic ternary polymer brush has the following general formula: A-g-(B-r-C-r-D).