The invention relates to an assessment method for penetrability of a plant liquid medicine canopy. The assessment method comprises the following steps: (1) by taking a multi-layer instrument shelter as a plant canopy model, inserting blades, regulating and recording quantity of blades at each layer, blade layer spacing, single-layer blade porosity, an interlayer blade arrangement mode and blade elastic modulus; (2) arranging water-sensitive paper on front and back surfaces of each blade; (3) vertically placing the multi-layer instrument shelter on a measuring point, performing liquid medicine spray experiment above the multi-layer instrument shelter, and recording wind speed of the canopy surface; (4) collecting the water-sensitive paper, and recording parameter information such as grain size of deposited fog drops and a rate of deposition; (5) processing data, and quantitatively analyzing a relationship between parameters. According to the assessment method, by regulating the parameters of the canopy perpendicular wind speed, the single-layer blade porosity, the blade layer spacing, the blade elastic modulus and the like, the correlation between a penetration rate of fog drops with different grain sizes and each parameter is analyzed and extracted, so that a theoretical direction is provided for required drug delivery dose for plant protection and a fog drop grain size range.