The Xi’an Branch of the Chinese Academy of Sciences (CAS) was first established in 1957. As an agency of the CAS in Shaanxi Province, the Xi’an Branch works jointly with the Shaanxi Academy of Sciences. The current president is Professor Ji Guo.
The Xi’an Branch of the CAS was formerly named the Northwest Branch of the CAS. Its Preparatory Committee which began in Xi’an in 1954, focused on organizing research institutes in the Northwest Region. In 1956, the Preparatory Committee of the CAS moved to Lanzhou, capital of Gansu Province, having an agency established in Xi’an. In 1957, the Xi’an Agency of the Preparatory Committee of the Northwest Branch was renamed the Xi’an Office of the CAS directly led by the CAS.　
In 1958, the Shaanxi Provincial Committee of the Communist Party of China decided to found the Shaanxi Branch of the CAS based on the Xi’an Office of the CAS. Its main responsibilities were to assist the CAS with the management of the research institutes of the CAS in Shaanxi and coordinate the work among other local research institutes. In April of the same year, the Shaanxi Branch of the CAS was officially established. In 1962, the Northwest Bureau of the Central Committee of the Communist Party of China decided to establish the Northwest Branch of the CAS, replacing the Shaanxi Branch and the Lanzhou Branch of the CAS. All the research institutes affiliated with the Shaanxi Branch were directed by the Northwest Branch.
　 After necessary adjustments, the rest of the institutes were either closed or moved to the universities. In 1962, the Northwest Branch moved from Lanzhou to Xi’an, which was closed in 1970. In 1978, with the approval of the State Council, the Xi’an Branch of the CAS was re-established, directed mainly by the CAS and partially by the Shaanxi Provincial Government.
　  The institutes of the Xi’an Branch of the CAS are the following: The Xi’an Institute of Optics and Precision Mechanics, the National Time Service Center; the Institute of Earth Environment; the Research Center of Soil and Water Conservation and Ecological Environment directed by both the Ministry of Education and the CAS. The key state-level research laboratories are: the State Key Laboratory for Technique of Transient Optics; the State Key Laboratory for Soil Erosion and Agriculture of Dry Land of Loess Plateau; the State Key Laboratory on Loess and the Quaternary Geology; the State Research Center on Technology of Water Saving Irrigation; the State Research Center for Water & Soil Conservation Engineering.
　  Key research fields involve: optoelectronics, optics & fine mechanics, transient optics, space optics, global environment, quaternary geology, petrology, conservation of soil and water, dry land agriculture, agricultural engineering of soil and water, high-precision time technology & service and electronics. Research of loess and global change of environment, transient optics, conservation of soil & water, and high precision time services has already reached advanced levels both in China and in the world. 
　  The Xi’an Branch of the CAS now has a total staff of 1391, among which 847 people are engaged in scientific research, 75 in administration, and 469 faculty workers. Among the science faculty, three are academicians of the CAS and one an academician of the Chinese Academy of Engineering (CAE). Four are regarded as state-level outstanding experts and five as province-level outstanding experts. Eighty-nine are research professors, 279 associate research professors and 290 assistant research professors. There are 19 people working as post-doctors at the post-doctoral station, and 137 people holding doctoral degrees and 140 master degrees.