The invention belongs to the technical field of biomass thermal energy conversion and utilization, and particularly relates to a biomass and coal coupling burning method. The biomass and coal couplingburning method comprises the following steps that (1) biomass is subjected to splitting decomposition through a two-stage type biomass continuous thermal decomposition device to generate biomass charcoal; (2) after the biomass charcoal is mixed with coal, a mixture enters a coal pulverizer and is pulverized into coal powder with the particle size of 20-50 [mu]m under the rotation speed of 25-100r/min, the pulverized coal powder mixed with the biomass charcoal enters a coal powder chamber and passes through a powder feeding machine and burns in a coal powder boiler through a coal powder burner, and heat supplying or power generation towards outside is realized; and (3) smoke discharged by coal power boiler in the step (2) is sampled through special equipment, the abundance of Carbon-14 inthe sample smoke is detected to determine the actual proportion of the biomass. According to the biomass and coal coupling burning method, the biomass and the coal burn in the coal powder boiler efficiently, and biomass and coal coupling burning proportion is obtained by detecting the content of the Carbon-14 in the smoke.