Abstract: 【Objective】The estimation of agricultural biomass resource is the key link and foundation to develop and utilize agricultural biomass scientifically. Straw returning could help maintaining and enhancing soil function, so the ecological potential assessment of agricultural biomass resource is the important prerequisite of sustainability using agricultural biomass. Thus, the main purpose of this article is, to consider the ecological requirements of agricultural soil, to assess the ecological available biomass energy potential from the main crops in different straw returning rate scenarios, and analyze the time-space characteristics and structural composition, to provide some suggestions for the development of agricultural biomass.【Method】Firstly, according to the national datum of crop planting area datum, the percentage ratio of each province and sown area, the main crops planting proportion and yield datum, using a linear regression method, expert prediction, to make predictions for the future 50 years; Secondly, based on the relative researches, the grass valley industrial using ratio, feed using ratio and burning ratio were designed; considering the soil ecological requirements and relative researches, using scenario analysis method, low crop remaining returning ratio scenario, medium crop remaining returning ratio scenario and high crop remaining returning ratio scenario were designed; Finally, from the perspective of spatial distribution and time distribution, to calculate and analyze the finally potential available biomass, and give some suggestions.【Result】(1) By 2050, in low crop remaining returning ratio scenario, medium crop remaining returning ratio scenario and high crop remaining returning ratio scenario, the final available biomass were respectively 162 million tons of standard coal equivalent, 78 million tons of standard coal equivalent and 11 million tons of standard coal equivalent. And as time goes on, the final available biomass of main crops will eventually have agglomeration on space, time and species composition. (2) In low and medium crop remaining returning ratio scenario, the space distribution of final biomass are mainly distributed in the northeast, East China, central China, besides Henan, Heilongjiang, Shandong and Xinjiang Province account most of the total; From the time aspect, it is mainly concentrated in August, September and October, and the rice, wheat and corn are the main sources. (3) In high crop remaining returning ratio scenario, from the space aspect, it mainly concentrated in East China, central China, South China and southwest China, besides Yunnan, Guangxi, Henan and Heilongjiang Province account most of the total; From the time aspect, it is mainly in January, February, November and December, from the component aspect, it is only made up of wheat, beans, potato and sugar cane.【Conclusion】Henan Province, Heilongjiang Province, Xinjiang Province and Shandong Province should be given priority when developing and using the biomass energy; Besides, when considering to build a regional crop straw distribution center, regional biomass energy industry base, large straw direct combustion power generation base, and some other large scale integrated agricultural biomass energy development projects, northeast China and central China could be given priority too. In addition, the biomass energy potential of southwest China, northwest China can be furthered through crop planting structure adjustment and improve the level of agricultural management.

Key words: biomass energy, crop stalks, main crop, renewable energy sources