The invention discloses a method for preparing a basic magnesium sulfate whisker/natural latex composite latex film. The method comprises the following steps of performing surface treatment on a basic magnesium sulfate whisker: performing modification treatment on the basic magnesium sulfate whisker, and performing ultrasonic dispersion and emulsion grafting polymerization to prepare PMMA (polymethyl methacrylate)-basic magnesium sulfate whisker particles; blending PMMA-basic magnesium sulfate whisker dispersion obtained by ultrasonic dispersion and MMA (methyl methacrylate) modified natural latex by adopting an emulsion-blending wet process, and performing direct film laying to prepare the basic magnesium sulfate whisker/natural latex composite latex film. According to the method, high performance such as higher structural integrity, mechanical strength approximate to theoretical strength of interatomic valence bond force and far stronger than that of various granular fillers which are commonly used at present, high length-diameter ratio and high heat resistance and flame retardance of the basic magnesium sulfate whisker is utilized, so that the comprehensive performance of the composite latex film is enhanced, and the prepared basic magnesium sulfate whisker/natural latex composite latex film is high in performance.