The invention relates to pebble coal transmission equipment for a heat-engine plant, in particular to a high-efficiency environment-friendly type negative-pressure pneumatic transmission system for pebble coals. The system of the invention comprises a plurality of pebble coal buckets connected with a coal grinding machine, wherein the pebble coal buckets are connected with the respective branch pipeline through feeding devices; each branch pipeline is lead into a pebble coal bunker through a main pipeline; a dumping device is arranged at the bottom of the pebble coal bunker; an air outlet at the upper part of the pebble coal bunker is connected with a volume air blower through a dust remover; the branch pipelines and the main pipeline comprise a plurality of horizontal pipelines and ascending pipelines; a transmission air pipe communicated with the outside atmosphere is arranged on each ascending pipeline; and a blowing tuyere communicated with the outside atmosphere is arranged on each horizontal pipeline. The invention has stable operation, difficult clogging, little dust pollution, small noise and strong transmitting capacity.