The under-frame of spectator stand adopts an American steel truss and the chain-type quick mount combination design system. In the aspect of construction, to eliminate the chance of mistakes we do not use the bolts in the process of installation. This approach might reduce the mistake rate to zero and guarantee 100% safety. After all, the safety is the first principle and the accident prevention is always considered. We design safety channels, non-slip floors and protective barriers, green and safe boarding ladders and street lamps flexibly. They are guaranteed in terms of safety for loading audience.