According to the setting in the novel, Xie Jingxing is five years older than Shen Miao.

The setting in Xie Jingxing's novel is that he has graduated from high school and worked hard in the society for several years, so he should be around 25 years old.

-Shen Miao just graduated from high school, and his age should be around twenty.

The above are the settings in the novel, and the specific age gap may be different according to the changes of different versions of the novel.