The utility model provides a narrowing spring locking excitation mechanism for an automatic injection pen, which comprises a push rod, a retraction sleeve, a narrowing spring base, a narrowing spring and the like, and is arranged around the narrowing spring, so that the locking can be ensured to be safe and cannot be easily triggered and unlocked; unlocking excitation can be achieved only when the push rod pushes
medicine to complete injection, pushing force is automatically provided by the needle retracting spring in the unlocking excitation process, dependence on the elastic force of the
tail section of the injection spring can be eliminated, and the unlocking excitation process is convenient and rapid.