The invention relates to azoxystrobin acetic acid solvate and a preparation method thereof. Its X-ray powder diffraction pattern is at diffraction angle 2θ=7.40±0.20°, 8.28±0.20°, 13.26±0.20°, 14.07±0.20°, 14.52±0.20°, 18.08±0.20°, 18.42±0.20°, 18.86±0.20 °, 20.46±0.20°, 21.18±0.20°, 22.14±0.20°, 22.68±0.20°, 24.46±0.20°, 26.88±0.20°, 28.60±0.20°, etc. have characteristic peaks, of which 7.40±0.20° is the starting point peak, the relative intensity of the characteristic peak at 21.18±0.20° is 100%. The preparation method is a constant-temperature suspension crystallization method, and the operation is simple, the reproducibility is good, the product has good fluidity, is not easy to coalesce, and is easy to be industrialized.