This is not as easy a question as you might think. I would say Nanking, since it was the capital from 1940 until 1949.
During 1949, however, the Chiang Kai-Shek-led Republic of China and the Mao Tse-Tun-led Communistsfought for control of the country, and as Mao's forces won more and more of the country, the capital of the Republic of China was shifted four times.
After Chiang's forces were defeated and his government retreated to Taiwan, the U.S. regarded his government as the "real" China(ignoring the Communist People's Republic of China, which governed hundreds of millions in mainland China)and regarded Taipei, the capital of Taiwan, as the capital of China. Eventually the U.S. recognized the existence of the PRC, but some people might argue that until then, the official capital of China in the view of the U.S. was Taipei.
The capital of the People's Republic of China since October 1949 (a couple months before the end of China's civil war) has always been Beijing.
I'll just mention that during WWII, which for China started in 1937, the site of the capital was Chongqing, and that China in some form or another has been in existence for over 25 centuries and so has had during that time dozens of capitals. However, since 1644, Beijing has been the capital for a large majority of the time, followed in frequency by Nanking.
Xi'an
Beijing. Peking was the old name of Beijing.
Almaty is the largest city in Kazakhstan, but the capital city is Astana (now called Nur-Sultan).
Yes, Peking, now known as Beijing, has been the capital of China for several dynasties and remains the capital today.
Beijing is the real name for the capital city of China. 'Peking' is the British form because of their poor chinese back in history. (I revise you, don't go walking around Chinese people and speaking about Beijing and calling it Peking instead. Some Chinese people either get offended or really irritated by this.)
Beijing, formerly known as Peking, is the capital of China. In Chinese, Beijing means 'northern capital'. It is sometimes mispronounced with a softer 'j', but its correct pronunciation is bǎy-jīng (as in 'jingle'). The political and cultural capital of China for hundreds of years, Beijing perhaps makes decisions for more people than any other capital city. Beijing is located on the western coast of China on the Pacific Ocean and stands at the northern tip of the North China Plain. The city is 39% flat land and the other 61% is quite mountainous area. Prior to Emperor Zhu Di, the capital was Shanghai.
Kyoto is the former capital, Tokyo is the current capital.
Thebes was the Egyptian capital.
If you have a very old map, look for 'Peking'.
Memphis was the capital of old kingdom Egypt.
Santa Fe is the capital city of New Mexico
Constantinople is the old, roman, name for the city now called Istanbul. It is the capitol of Turkey.