As a young man, Guo studied at the Yuelu Academy in Changsha, where befriended Zeng Guofan. In 1847, Guo was awarded the highest degree in the and soon afterwards he became a bachelor in the Hanlin Academy. In 1853, he was called to assist Zeng Guofan suppressing the Taiping Rebellion in their native province of Hunan. During the suppression of the Taipings Rebellion, Guo distinguished himself as a prominent advocate of the local likin tax as a means of financing the campaigns. He later also assisted Li Hongzhang's Huai Army in their campaigns against rebels in the Anhui province.
Guo became an important member of China's Self-Strengthening Movement in the 1860s and 70s and distinguished himself for his advocacy of a moderate and peaceful foreign policy. Guo became the first Qing to be stationed in a western country. He served as an ambassador to England and France from 1877 through 1879 as part of England's demands after the Margary Affair to have a Chinese Ambassador in England.