Which one is more formal, China Travel Service or China Travel Service?

Both travel agencies are formal.

China Travel Service (China International Travel Service) is a state-owned enterprise directly managed by China Travel Service Corporation and is one of the largest international travel agencies in China. China Travel Service has extensive tourism resources, professional teams and rich tourism products at home and abroad. Its business scope includes domestic tourism, outbound tourism, inbound tourism, exhibition tourism, etc.

CITS (China International Travel Service Co., Ltd.) is China’s first listed tourism company and one of the largest comprehensive travel agencies in China. CITS has a wide range of branches and travel agency outlets at home and abroad, providing a variety of tourism services, including domestic tourism, outbound tourism, inbound tourism, exhibition tourism, etc.