This drama interprets the true meaning of life of love and being loved, happiness and struggle by telling the struggle history of the protagonist Huang Zili. Huang Zili, who has been studying hard and working hard for ten years, has fallen to the bottom of his life due to a series of heavy blows. However, he did not succumb to the arrangement of fate, and always insisted on striving forward in difficult adversities. Because of a misunderstanding, he met the female policeman Fang Yan. After getting along, Fang Yan would take the initiative to take care of Huang Zili's family after get off work in order not to distract Huang Zili. In the process of getting along, the two people developed a strong liking for each other. Huang Zili had a premonition that happiness had finally arrived, and finally won a wonderful life. "Happiness Will Knock on the Door" is a TV series that promotes the main theme and conveys positive energy. It interprets the theme of "people's yearning for a better life". The whole play is based on the story of the male and female protagonists, showing the core value of "happiness is struggled for", showing the positive energy quality drama of the struggle stories of ordinary people, and inspiring people to rely on their own efforts to strive for happiness.