It means adding flowers to a beautiful brocade fabric. The metaphor is slightly modified, and the beauty is more beautiful. The extended metaphor is further improved on the basis of the original results. From Huang Songting-zhang's Ode to Ancestors: "Fu Weng wants to eulogize again, and the picture is icing on the cake." In addition, Qing's Huang Ranfeng: "The Third Lady congratulates her on becoming the first lady, entering a brand-new house and releasing her usual ill feelings. It's really icing on the cake. " Mao Zedong's speech at the Yan 'an Forum on Literature and Art II: "For them, the first step is not icing on the cake, but offering timely help. Therefore, under the current conditions, the task of popularization is more urgent. "