300 series biomass gas engines including two models 6300 and 8300, the flammable gas of which is produced by gas firing kiln using rice hull, straw and wood scraps as feedstock. For the low heat and excessive tar of biomass gas, many improvement has been made and now they have reached a high tech level and process the characteristics such as compact structure, easy operation, reasonable arrangement and easy maintenance etc. Types of the engines are mainly use in land generating sets, includes two kinds of frequencies 50Hz and 60Hz, and both single set running and multiple sets parallel running are OK.