Wood pellet is one of biomass energy fuels, which is produced by compressing woody biomass such as sawdust, planer shavings, and whole-tree removal or tree tops and branches leftover after logging into cylindrical form. Latterly much attention has been paid to wood pellet boiler which is suitable for use at various scales in domestic and industrial furnaces for heat production to replace conventional fossil fuel energy sources since the use of wood pellet that is carbon neutral can alleviate global warming. This study presents the result of developing a high efficiency wood pellet boiler with 55MJ/h capacity. Efficiency has been improved by using a rotating disk burner with a shorter screw feeder. Special attention has been paid to the improvement of the safety of the wood pellet boiler from backfire by adopting a double protecting system composed of a shutter and an air curtain. The result shows that the efficiencies of the wood pellet boiler are 97.2% and 89.2% based on lower and higher heating values, respectively, at 15.1kW of heating output.