NOVELTY - Fertilizer is produced by mixing condensed sludge obtained from biological treatment of organic wastewater with plant straw powder and cooking reagent, heating to 125-170 degrees C and keeping for 2-7 hours to obtain slurry of organic fertilizer, and drying to obtain granular or powder organic fertilizer, adding chemical fertilizer to slurry and drying to obtain organic-inorganic composite fertilizer, or filtering slurry to obtain filter liquid having humic acid content of 5-15% and adding potassium or ammonia nitrogen fertilizer to obtain organic potassium or organic ammonia liquid fertilizer.    USE - Method for producing fertilizer (claimed).    ADVANTAGE - The method has simple operation, quick sludge decomposition speed, achieves sludge and waste plant straw utilization on large-scale and at low cost, and obtains fertilizer having high organic substance and humic acid content.    DETAILED DESCRIPTION - Fertilizer is produced by:    (A) mixing condensed sludge obtained from biological treatment of organic wastewater with plant straw powder at mass ratio of 20:(1-5) and cooking reagent comprising ammonium sulfite, sodium sulfite and/or potassium bisulfite at dose of 8-15% dry weight of mixture, stirring uniformly and loading in pressure-resisting and high-temperature-resisting container;    (B) heating to 125-170 degrees C through steam or external heat source, and keeping for 2-7 hours while rotating container slowly to obtain slurry of organic fertilizer; and    (C) drying to obtain granular or powder organic fertilizer;    (D) adding chemical fertilizer to slurry to have total amount of nitrogen, phosphorus, potassium, sulfur and trace elements of 15-30% and drying to obtain granular or powder organic-inorganic composite fertilizer; or    (E) flat-frame filtering or centrifugal filtering slurry to obtain filter liquid having humic acid content of 5-15%, and adding potassium fertilizer comprising potassium nitrate, potassium sulfate or potassium chloride to obtaining organic potassium liquid fertilizer or adding ammonia nitrogen fertilizers to obtain organic ammonia liquid fertilizer.