The structure of the baojia system changed over time. In Wang Anshi's original system, its basic unit was the bao (watch), which consisted of ten families. However, during the Ming Dynasty, this ten family unit was instead labeled a jia(tithing), and ten jia (or one hundred families) made a bao. Each jia possessed a placard that rotated among the families. The family holding it at a given time was the jiazhang, or tithing captain. Similarly, the captain of the bao was the baozhang.

There was a great deal of regional variation in the system. In some areas, jia had as few as four families or as many as thirteen. Some Jiangnan counties added an intermediary unit called the dang (compact}. This unit consisted of thirty families and had a corresponding dangzhang.

During the Qing Dynasty, the system's structure changed again. Ten households made up one pai, ten pai constituted one jia, and every ten jia formed a bao. Studies by Philip Huang and Wang Fuming of Baodi County in northeastern Hebei province (now Baodi District, Tianjin) have shown that the lowest quasi-official was the xiangbao, who oversaw about twenty villages and was intended to act as a buffer between the people and the government.

When the system was reimplemented in the Republic of China, the structure remained essentially the same, with the exception of the introduction of the lianbao (associated bao), a group of several bao at the district level.