Abstract: Tobacco stem was used as a major fermentation substrate under solid-state fermentation by Aspergillus niger h1. Fermentation conditions were optimized based on the pectin residual rate in tobacco stem after fermentation and the orthogonal test was carried out. The optimized fermentation showed as follows:the ratio of dry tobacoo stem to water was 1∶1.2, 40g of tobacco stem was put in a 1000mL triangular flask with inoculum 20%, and the fermentation was carried out at temperature 30℃ for 6d. Under above conditions, the verification test was made and the pectin residual rate in tobacco stem after fermentation was 27.32% . Pilot scale experiements were carried out in a 150L thick layer ventilation solid-state fermentation reactor , and after fermentation and enzyme hydrolysis, the residual rates of macromolecular substances, such as pectin, starch or protein in residual tobacco stem were 35.19%, 25.06% and 58.74%, respectively, indicating most of macromolecular substances in the tobacco stem could be degraded and dissolved in water. So that, macromolecular substances could be degraded well by solid-state fermentation.