The invention provides a biomass-biomass briquette combined gasification-combustion boiler based on a parallel circulating fluidized bed, relates to a multi-fuel circulating fluidized bed boiler, andsolves the problems that an existing circulating fluidized bed boiler adopts single burning fuel, waste heat utilization after fuel burning is insufficient and more environmental pollutants are emitted. The fluidized bed of the boiler is divided into two parallel areas, and burning of biomass briquette and gasification of biomass can be carried out in the separate beds, so that emission of the environmental pollutants such as nitrogen oxide, carbon dioxide, sulfur-phosphorus oxide and the like is reduced. The biomass briquette is formed by biomass waste particles of straw and rice husks and pulverized coal particles through mixing in a ratio being 7:3 or 5:5. A certain bending radian is formed at the upper part of a partition of the two beds and has a draining effect on a material. High-temperature particles produced by burning of fuel in a bed 1 overflow to a bed 2 during fluidifying, carbon residues produced after gasification reaction in the bed 2 are recovered and sent into the bed1 for continuous burning, an inner circulation is formed, and accordingly, heat produced by the reactions is sufficiently utilized.