The invention discloses a whisker strengthening toughening halogen-free flame retardance phenolic aldehyde foamed plastic and a preparation method thereof. The plastic is prepared from, by weight, 100 parts of expandable phenolic resin, 1-5 parts of flexibilizer, 5-10 parts of surface active agent, 15 parts of foaming agent, 15 parts of curing agent, 3-10 parts of flame retardant and 1-5 parts of whisker fortifier. The invention further discloses the preparation method of the flame retardance toughening phenolic aldehyde foamed plastic. According to the plastic, intensity and toughness of the phenolic aldehyde foamed plastic are improved by using a few whiskers, the flame retardance property of the foamed plastic is improved by adding composite flame retardant, meanwhile the flame retardant of the phenolic aldehyde foamed plastic is further improved by adopting the new compound emulsifier, wherein the compression strength is higher than 0.2MPa, the heat conductivity coefficient is lower than 0.04W / m*k, the oxygen index is larger than 50%, the scaling-off rate is lower than 3%, and the flame retardance property (DIN 4102) reaches grade A; the plastic is a halogen-free flame retardance phenolic aldehyde foamed plastic with excellent comprehensive performance, the plastic can be applied to heat preservation field such as architecture, and fire prevention safety of heat preservation in building is greatly improved.