Small-pitch LED display screens are widely used, including command and dispatch centers, security monitoring, video conferences, exhibitions, radio and television studios, meteorological information centers, safety production monitoring, environmental monitoring, fire fighting, maritime flood control command, energy, electricity, financial securities markets, airports, subways, shopping malls, hotels and so on. At present, the small-pitch LED display screen is mainly used in indoor professional display field, with an area exceeding 100 inch.