Abstract: Some properties，structures as well as stability of three different forms of crystalline phosphorus pentoxide(P₂O₅)，including o-，o′-，and h-P₂O₅ under normal atmosphere were introduced.In order to obtain a phosphorus pentoxide crystal who had a stable evaporation rate，the raw material orthogonal orthorhombic type o-P₂O₅ was directly heated by muffle furnace.Through the experiment, it was found that the initial evaporation rate of o-P₂O₅ was too fast to control, but when o-P₂O₅ was heated till it transformed into hexagonal crystal h-P₂O₅，the evaporation rate bacome stable.Therefore，the next operation will be very easy when h-P₂O₅ was applied.

Key words: phosphorus pentoxide, crystal transformation, structure, stability