The invention discloses a fitness device for training arm strength. The fitness device structurally comprises two reinforcement plates, a first waterproof cover, a connecting arm, a climbing wheel, asecond waterproof cover, a locking screw, a safety protection device, a center gear, a positioning and mounting screw and a lower bottom plate, the first waterproof cover is fastened at the left top end of the safety protection device through a fastener, the two reinforcement plates are clung at two inner ends of the safety protection device, and the locking screw penetrates the safety protectiondevice and is connected with the reinforcement plates in a threaded manner. The device is provided with the safety protection device, the safety protection device can timely eject an ambulance plate when an accident happens in the training process of a trainer, so that the trainer cannot directly fall onto the ground, a buffering function is achieved, injury to the trainer is reduced, training safety is improved, the trainer can train with might and main, and training effects are better.