The son of a jurist, Rho entered the Society of Jesus at the age of twenty. While later proficient in mathematics, he was a poor student initially.
Following his ordination in Rome by Cardinal Bellarmine, he sailed for the Far East in 1617 with forty-four companions. After a brief stay in Goa he proceeded to Macao. During the siege of that city by Dutch forces, he taught the inhabitants the best use of artillery, and saved it from the attack. This service opened China to him.
Rho rapidly acquired a knowledge of the Chinese language and in 1631 he was summoned to Beijing by the emperor to work on reform of the Chinese calendar. Together with Johann Adam Schall von Bell, he occupied himself on this task until the end of his life seven years later, in 1638. Numerous Chinese officials attended his funeral.
- This article incorporates text from a publication now in the public domain: Herbermann, Charles, ed. (1913). "Giacomo Rho". Catholic Encyclopedia. Robert Appleton Company. The entry cites: