The third time was not the Rongguo mansion, but after Jia's defeat, Grandma Liu went to the prison to visit the owner of the Rongguo mansion, then rescued her, raised her and married her. Granny Liu described the luxurious life of this restaurant through what she saw and heard in the Rong Guo Mansion three times, pointed out the disparity between the rich and the poor at that time, and exposed and criticized the sin and luxury of the feudal aristocratic life at that time. It reflects the inevitable collapse trend of Jia family in the increasing class struggle. It can be said that granny Liu, as a third party, is a witness to the rise and fall of Jiafu. He played a different role three times: for the first time, Xifeng told her poor relatives about the "catastrophe". But at that time, the Jia family was still a hundred-legged worm. The so-called "pulling a hair is thicker than grandma Liu's waist." The second time, she wrote that Jia Fu was still in the dead-end stage and the banquet was still very lively. The descriptions of the first and second items introduce the prosperity and luxury of Jia Fu and many major figures. After entering the mansion for the third time, Jia Fu collapsed completely, so Xifeng had to entrust the orphan to Granny Liu and ask her to take care of her only daughter. Through the comparison and description of Granny Liu's third assignment, this paper points out the three stages of Jia's rise and fall. Granny Liu is a witness to the decline of Jiafu. Judging from the life picture depicted by Granny Liu's three visits to Guo Rongfu, not only economically, but also politically, it shows that the feudal class is bound to decline and the feudal society is bound to collapse.