The invention relates to the pneumatic conveying technology, and discloses a pneumatic limestone powder conveying system. The pneumatic limestone powder conveying system specifically comprises a boiler, powder pipes and bin pumps. The powder pipes include the first-level large powder pipes and the first-level small powder pipes. The bin pumps include the large bin pump and the small bin pump. The large bin pump is connected with the first-level large powder pipes. The first-level large powder pipes are diverted by distributors into N second-level large powder pipes. The small bin pump is connected with the first-level small powder pipes. The first-level small powder pipes are diverted by distributors into N second-level small powder pipes. N is a natural number larger than one. Large powder adding ports and small powder adding ports are formed in the left side and the right side of the boiler, wherein the number of the large powder adding ports in the left side of the boiler is equal to the number of the large powder adding ports in the right side of the boiler, and the number of the small powder adding ports in the left side of the boiler is equal to the number of the small powder adding ports in the right side of the boiler. The large powder adding ports are connected with the second-level large powder pipes, and the small powder charging ports are connected with the second-level small powder pipes. The invention further discloses a control method of the above system. According to the different situations of work conditions, pneumatic conveying is conducted by adopting large pipelines or small pipelines or a manner of matching of the large pipelines and the small pipelines.