In this paper, considering the emergency braking problem for double pendulum crane systems, we propose a swing suppression guaranteed braking method with safety limits consideration, whose performance is also theoretically proved. Since the workspace for double pendulum cranes may be complex, while the transported payload may be large, it is of great significance to design proper emergency braking methods to make the entire double pendulum crane brake quickly and avoid possible accidents. By carefully analyzing the crane dynamics and taking into account the important swing suppression objective, coupling enhanced terms are designed based on the coupling behavior between the trolley motion and the swing angles. Then the coupling enhanced terms are combined with crane mechanical energy function, which further introduces swing angle-related feedback terms and achieves better swing suppression performance. Furthermore, safety limits are also taken into consideration by designing a special barrier function-like term, which can restrict the payload and hook horizontal positions in permitted domains. Based on all these terms, the swing suppression guaranteed braking method is designed with rigorous mathematical analysis proposed to shown its proper performance. To the best of our knowledge, it is the first emergency braking method for double pendulum cranes. Experimental tests are also implemented by using a hardware crane testbed, which further verify the effectiveness of the proposed method.