Most visitors will require a visa to enter China on business or leisure trips. Different documents are needed depending on which country you are traveling from, and for what purpose. Please see here for detailed information relating to your home country to http://www.visaforchina.org/.
Beijing, Tianjin and Heibei offer 144-hour visa-free transit for foreign visitors holding third-country visas when they land at one of these cities - perfect for a short sightseeing trip while on your way to another part of the world.
Foreign visitors who hold passports issued by the countries on the 144-hour visa-free transit policy list and stay in Beijing, TianJin or HeiBei for transit for up to 144 hours can apply for a visa-free transit stay in China at the immigration inspection authority at Beijing Capital International Airport. This policy is only applicable for foreign visitors who enter into, stay in and leave from Beijing before traveling onwards to another destination.