The database method,a new mask design method is presented,which is based on the color-equivalent-gray theory.Choosing different values of red,green and blue to form different colors,masks composed of these colors can be obtained by color film recorder.The output mask is used to linearly modulate the exposure.Consequently,the linearization of steps can be realized.The theoretical calculation and the experimental result of sixteen-step Fresnel are given.As a result,the database method is feasible.It provides a new approach for the gray expansion and has some referential meaning for the fabrication of DOEs.