Abstract: The effect of substrate concentration on photo-fermentation hydrogen production by HAU-M1 via simultaneous saccharification fermentation using Paulownia leaves as the substrate was studied.Taking cumulative hydrogen production and hydrogen production rate as assessment indicators,the photo-fermentation hydrogen production capabilities from leaves with different substrate concentrations are discussed.The variation of pH and reducing sugar concentration under different conditions is analyzed.It is found that the maximum cumulative hydrogen yield of 167.85 mL is obtained at substrate concentration 25 g/L,corresponding with the hydrogen content of 39.5%,and the maximum hydrogen production rate of 5.42 mL/h is obtained at 36 h.The hydrogen production cycle of Paulownia leaves is 72 hours,the peak period of hydrogen production is concentrated in 24-60 h.When the reaction proceeded from0-12 h.The reducing sugar concentration of the reaction solution increased rapidly,then gradually decreased after 12 h,and kept stable at last.The kinetics of hydrogen production under different substrates concentration are analyzed by using the modified Gompertz equation.The results showed that Paulownia leaves could be used as the substrate for photosynthetic hydrogen production.The maximum cumulative hydrogen yield and hydrogen production rate are achieved at substrate concentration 25 g/L,which are 168.79 mL and 6.51 mL/h,respectively.