Zhang Heng (78-139) was born in Ping Zi. Han nationality, a native of Xi 'e, Nanyang (now stonebridge, Nanyang City, Henan Province), is one of the five saints in Nanyang, and is also known as the four masters of Han Fu with Sima Xiangru, Yang Xiong and Ban Gu. China was a great astronomer, mathematician, inventor, geographer and writer in the Eastern Han Dynasty.

In the Eastern Han Dynasty, he served as a Langzhong, Taishiling, Shizhong and Hejian. Zhang Heng made outstanding contributions to the development of astronomy, mechanical technology and seismology in China, and invented the armillary sphere and seismograph, which was one of the representatives of the theory of armillary sphere in the middle of the Eastern Han Dynasty. It was praised by later generations as "wood saint" (branch saint). He is the author of Lingxian, Illustrated Notes on Hunyi, etc., and his mathematical works are On Calculation, and his literary works are represented by Erjing Fu and Guitian Fu. Sui Shu Jing Ji Zhi has 14 volumes of Zhang Hengji, which has been lost for a long time. Zhang Pu, a Ming Dynasty, compiled Zhang Hejian Collection, which was included in 13 Collection of Han, Wei and Six Dynasties.

In his later years, he entered the court as a minister of history due to illness. Yu Yonghe died in 139, at the age of 62. In the Northern Song Dynasty, it was named Xi 'erbo.