A method for making a cushioning air bag with a predetermined opening in an air cylinder turning zone, including: providing an air cylinder sheet; adhering the two sheets of outer film to form turning points; determining a turning middle line on the air cylinder sheet; configuring nodes on two respective sides of the turning middle line; turning the air cylinder sheet along the turning middle line; and adhering two sides of the turned air cylinder sheet with lateral heat sealing lines; wherein two lateral sides of the air cylinder sheet between nodes and the turning middle line form a non-heat sealing section; a bottom surface is formed between turning points, the non-heat sealing section of the turning zone is expanded to form a lateral polygonal opening, and a supporting surface is formed on a bottom of the opening, after the air cylinder sheet is filled with air.