The invention discloses a pretreatment method for detecting metallic elements in a kapok water extract. The pretreatment method comprises the following steps of firstly, placing the kapok water extract into a digestion tank, adding nitric acid with mass fraction of 15 percent, and then placing into a digestion instrument for performing microwave digestion; secondly, transferring a digestion sample liquid in the digestion tank into a teflon crucible, washing the digestion tank with ultrapure water, mixing all washing liquid into the teflon crucible, and heating the teflon crucible to remove acid; thirdly, after the teflon crucible is cooled to room temperature, completely transferring the liquid in the teflon crucible into a volumetric flask, washing the teflon crucible with the ultrapure water, mixing all washing liquid into the volumetric flask, and then using nitric acid with mass fraction of 2 percent to fix the volume. Compared with traditional open methods such as an ashing method and a heating acid digestion method, the pretreatment method has the characteristics of short time consumption, less reagent consumption, thorough digestion, less interference of organic matters during detection and good reproducibility.