Abstract: The present invention provides an anti-misfit structure for a nail cartridge, which resolves the problems of a typical nail cartridge. For example, when a short collated nail is mistakenly inserted, it is likely lead to different triggering strength, and easier swinging and jamming of nail bodies against stability and safety. The swinging end of the spring of the nail cartridge is provided with a stopper. So, when the nailer head of a short collated nail is mistakenly inserted into the long nailer head dent, the stopper blocks the collated nail, thus preventing any misalignment and subsequent triggering of a nailer for higher stability and safety.