The invention relates to an injection auxiliary device matched with an insulin injection pen. The injection auxiliary device comprises an outer barrel and an inner barrel and is characterized in that a lower absorbing end, a gasket and a groove are arranged on the outer barrel; the lower absorbing end is located at the bottom of the outer barrel; the gasket is arranged at the bottom of the lower absorbing end; and the groove is located on the inner side of the outer barrel. The injection auxiliary device has the characteristics of simple structure, convenience in operation, economical and practical effects, high applicability, low cost and the like, and can be conveniently put into the market and produced in batches. The device can assist the insulin injection pen in quickly injecting by utilizing the magnetic force, the injection time is shortened, a patient can be helped to more accurately inject insulin, and the pain of the diabetic patient caused by insulin injection can be greatly relieved.