Because Zheng Yaomei swore when she died that she would never marry Liu Damao.

Zheng Yaomei likes Liu Damao, and Liu Damao likes Zheng Yaomei in Southwest China, but Zheng Yaomei has been married three times, and every time the groom is not Liu Damao she likes. It's a long story In the thirteenth episode of TV series, Zheng Yaomei died after giving birth to Xu's child. The old lady suspected that the child was not promised because of the instigation of her aunt. In order to make Xu blind, Yao Mei swore before the coffin that she and Liu Damao had never had an affair and would never marry Liu Damao.