Cantilever crane contains a curved arm type cantilever crane, fixed column type cantilever crane, mobile cantilever crane, double arm cantilever crane, although they have different names, but they also have common characteristics. For example, the footprint is also small, high efficiency, high reliability in the use of the time, very suitable for short distance lifting and transportation, the use of frequency is also very high, and all can carry out more intensive lifting work.