A preparation method of low-As-content tree moss absolute oil comprises the following specific steps that 1, a tree moss raw material is soaked with water of 15-30 times of the amount of the tree moss raw material for 0.5 -2 hours, the soaked tree moss raw material is naturally air-dried, 100-mesh screening is performed after smashing, extraction is performed by using 65%-95% ethyl alcohol or petroleum ether, an extract is concentrated till no solvent is evaporated after extraction, and tree moss extract is obtained; 2, 95% ethyl alcohol 3-6 times of the mass of the extract is added to the tree moss extract for redissolution, freezing is performed at the temperature of 10-30 DEG C for 8-24 hours after full stirring and dissolution, insoluble substances are filtered out, the solution is concentrated till no solvent is dissolved, and the low-As-content tree moss absolute oil is obtained. The preparation method has the advantages that the operation is simple, the As content in the tree moss absolute oil is reduced under the coordinating effect of two treatment processes, no adverse influence is produced on the perfume quality of the final tree moss extract, the fragrance is purer, and the product quality is better. In addition, a preparation method is low in cost and suitable for large-scale industrial production.