Introduction to China Football Association League A:China League One (hereinafter referred to as "China League One") is the second level professional football league organized by China Football Association and participated by domestic professional football clubs, second only to the Super League of China Football Association.The Chinese Football League A began in 2004, formerly known as the Chinese Football League A.In the first session, 17 teams participated in the promotion and demotion system.In 2020, the Chinese League A will expand to 18 teams