Passengers in transit are allowed 72 hours without a visa. Otherwise, visas are required for almost all nationals. A 30-day visa is standard. One extension is usually possible. Citizens of 51 countries, including Australia, France, Germany, the UK and the USA, are allowed to stay for up to 72 hours in Běijīng without a visa, as long as they have an onward travel ticket to another country.
You can find all information at the official website: http://www.visaforchina.org/
Welcome to a capital city whose story goes back at least 3000 years. In Beijing, you'll find a wealth of history, both ancient (the Hall of Preserving Harmony, Summer Palace, Forbidden City) and more recent (Chairman Mao Memorial Hall, Tiananmen Square). For the best market experience, choose the Dirt Market over the touristy Silk Market. A visit to the Great Wall, the longest manmade structure in the world, is absolutely essential.