NOVELTY - Preparation of photosynthetic bacterium preparation comprises slant seed activation culture by inoculating Rhodopseudomonas palustris into slant solid culture medium; shaking bed seed culture by inoculating activated strain into liquid culture medium and culturing for 36-48 hours at 32-34 degrees C; and ventilation fermentation tank culture by inoculating seed culture liquid (6-10 hundred millions/ml, according to 10-12% inoculation amount), and under black condition, culturing for 36-48 hours at 32-34 degrees C and 1.0-2.0 mg/L dissolved oxygen.    USE - Process of preparing photosynthetic bacterium preparation (claimed) useful e.g. in aquiculture, wastewater treatment, and crop farming.    ADVANTAGE - The process provides photosynthetic bacterium preparation having concentration of up to 40-60 hundred millions/ml.    DETAILED DESCRIPTION - Preparation of photosynthetic bacterium preparation comprises slant seed activation culture by inoculating R. palustris into slant solid culture medium to carry out activation; shaking bed seed culture by inoculating activated strain into liquid culture medium, and culturing for 36-48 hours at 32-34 degrees C, obtaining seed culture liquid; and ventilation fermentation tank culture by inoculating seed culture liquid (6-10 hundred millions/ml, according to 10-12% inoculation amount), and under black condition, culturing for 36-48 hours at 32-34 degrees C and 1.0-2.0 mg/L dissolved oxygen, obtaining photosynthetic bacterium preparation. The basic culture medium used in shaking bed seed culture and ventilation fermentation tank culture contains (wt.%): glucose (0.9-1.1), urea (0.04-0.06), dipotassium hydrogen phosphate (K2HPO4) (0.02-0.03), potassium dihydrogen phosphate (KH2PO4) (0.02-0.03), magnesium sulfate heptahydrate (MgSO4.7H2O) (0.02-0.03), sodium chloride (0.20-0.30), calcium chloride (CaCl2) (0.03-0.05), and water (98.40-98.77). Fulvic acid (0.10-0.30%) is added based on the basic culture medium. The culture medium used in slant seed activation culture is solid culture medium formed by adding constant amount of agar in the liquid culture medium used in shaking bed seed culture and ventilation fermentation tank culture.