Abstract: The soybean biological dissociation hydrolysate was studied,and the biological dissociation concentrated protein powder was obtained at the spray-drying inlet temperature 140,150,160,170,180,190 and 200 ℃. Changes of particle size distribution,microscopic morphology,contents of protein secondary structure,and microenvironment of concentrated protein powder were analyzed. The results showed that the particle size and average particle size of the concentrated protein powder obtained by biological dissociation increased with the increasing of the spray drying inlet temperature. When the inlet temperature was 200 ℃,the average particle size was 3.94 μm at the maximum. Under the scanning electron microscope,the concentrated protein powder was spherical,the surface layer had dents and wrinkles,and the larger of the particle,the smoother of the surface. The higher the spray drying inlet temperature,the larger the particles were. The secondary structure of the protein in the concentrated protein powder mainly contained β-sheet structure and irregular curl. When the inlet temperature was 150 ℃,the β-fold content was the highest. And when the inlet temperature was 180 ℃,the irregular curl content was the highest. Fluorescence spectrum analysis showed that the temperature of spray-drying inlet had no significant effect on the spatial structure of tryptophan around concentrated protein powder.