The invention provides a biological gas production system for filling straws in a mine goaf. The biological gas production system comprises a hot water entering well, a water returning well, a temperature monitoring well, an exogenous bacterium injection and bacterium colony monitoring well and a biological gas collection and conveying well which are formed above the mine goaf and are communicated with the ground, wherein heat insulation pipelines, which are made of stainless steel or an aluminum alloy material, are paved on the ground in the goaf in a crisscrossing manner; a residual heat water discharge pipe of a thermal power plant penetrates through the hot water entering well and stretches into the goaf to be connected with water inlets of the heat insulation pipelines; water outlets of the heat insulation pipelines are connected with a water returning pipe; the water returning pipe upward penetrates through the water returning well, and then is returned back to the thermal power plant; and the goaf is internally filled with crushed straws. The invention further discloses a gas production process of the biological gas production system for filling the straws in the mine goaf. According to the biological gas production system and the gas production process, provided by the invention, a good space advantage of the mine goaf is utilized, and the aim of green mining of mines is realized; and meanwhile, the straws are converted into a clean energy source by utilizing a biotechnology, and energy consumption and emission reduction are realized.