It was erected as an apostolic vicariate on 10 August 1926, comprising five civil sub-prefectures Ningpo (v.) and entrusted to the care of the “Patres Sinenses Congregationis Missionis,” i.e., the Chinese Lazarists of the regular province of southern China. On 11 April 1946, with the establishment of the episcopal hierarchy in China, it was elevated to a suffragan diocese of Hangchow.
It covers an area of 3,135 sq. km. As of 30 June 1948, with a total population of approximately 2,000,000, there were 7,813 Catholics and 383 catechumens; 15 priests; 8 seminarians, of whom 4 were major; 35 sisters, all Chinese; and 49 catechists. Among the works were one orphanage, three dispensaries, one hospice for the elderly, and fifteen elementary schools.
The first missionary activity in the territory of Taichow was undertaken by the Chinese Lazarist priest Fou, who was invited there in 1867 by two compatriots, the only Christians in the area. In 1869, the Rev. Sin, a Chinese secular priest, was sent from Ningpo but died of cholera one month after his arrival. In February 1870, a third priest arrived, the Italian Lazarist Rizzi. By the time of their deaths in the same year (1890), Fou and Rizzi had left 190 Catholics. The bodies of these three first missionaries rest side by side in the oratory of Sao-Tchao. Subsequently, foreign and indigenous Lazarists arrived, and evangelization progressed: places of worship were multiplied, the work of the Holy Childhood was expanded, directed by indigenous virgins of the Association of Purgatory, and the territory eventually passed into the care of the local clergy.