It is very important to explore the damage evolution mechanism of wood under tensile loading at meso-scale，which is the foundation of establishing the damage constitutive model. In this paper，the component characteristics of wood at both macro and meso-scale were analyzed，based on the assumption that wood is equivalent to numerous tension fibers in parallel and every tension wood fiber is equivalent to an elastic brittle tensile micro-spring. The damage evolution equation was derived based on the assumption that the ultimate strains of tensile micro-springs are random variables that obey some form of distribution. Based on the correct setting of acoustic emission parameters PDT，HDT and HLT，the parameters of the ultimate strain distribution function were obtained by tensile acoustic emission tests on Northeast Larch wood specimens along the grain during the failure process. Furthermore，the damage evolution model was established.The analyzing results show a good coherence between the acoustic emission accumulative events and the damage evolution，and the acoustic emission tests are available for the damage assessment during the wood longitudinal tensile process.