Stall/spin has always been the most serious safety problem faced by general aviation aircraft in left boundary of flight envelope. The statistics of stall/spin accidents show that, the catastrophic consequences of stall/spin cannot be avoided although the aircraft has the ability to recover from spin. The text explains the concept of "layered defenses", and analyzes the requirements of stall/spin in the new FAR-23 airworthiness standards and the accepted compliance methods based on this concept. The construction method of a multiple defense system for the safety of general aviation aircraft in left boundary of flight envelope are proposed by improving the pilot"s state awareness, enhancing the aircraft"s departure resistance and reducing the damage of loss of control which will help general aviation aircraft better meet the requirements of the stall/spin airworthiness standards, and achieve the purpose of improving flight safety in left boundary of flight envelope.