The present invention discloses a spirooxazine photochromic exterior wall coating, comprising the following components by mass percent: 0.6%-1.5% of spirooxazine photochromic compound, 40%-45% of resin, 0.3%-1% of dispersant, 0.2%-0.3% of antifoamer, 1%-3% of additive, 22%-24% of pigment and 30%-32% of solvent. The additive comprises 0.9 wt %-2 wt % of NaCl or KCl solution. The present invention further provides a preparation method for the spirooxazine photochromic exterior wall coating, comprising measuring, grinding, dispersing, mixing, adjusting pH and filtering. Experiments prove that the spirooxazine photochromic exterior wall coating provided by the present invention has good light fatigue resistance effect and can meet the needs of long-term use of building exterior walls.