NOVELTY - The production of crotonaldehyde involves feeding acetaldehyde to condensation tower, adding boiling water to aldol dehydration tower, adding tetramethylammonium hydroxide as catalyst, adding catalyst solution, acetaldehyde and acetic acid to condensation tower, performing aldol reaction, reflux condensing, discharging 3-hydroxybutyraldehyde into aldol dehydration tower, dehydrating to obtain crotonaldehyde, condensing tower top distillation product, recycling acetaldehyde gas condensate to condensation tower and recovering crotonaldehyde.    USE - Production of crotonaldehyde (claimed).    ADVANTAGE - The method enables environmentally-friendly production of crotonaldehyde with zero discharge of wastewater.    DETAILED DESCRIPTION - The production of crotonaldehyde involves feeding acetaldehyde to condensation tower, adding boiling water to aldol dehydration tower, adding tetramethylammonium hydroxide as catalyst, adding catalyst solution, acetaldehyde and acetic acid to condensation tower in molar ratio of 1:1000:5, performing aldol reaction at 42-49 degrees C and pressure of 0.05 MPa, reflux condensing, adjusting amount of acetic acid to achieve liquid acidity of 0.06-0.08 mol/l, discharging obtained 3-hydroxybutyraldehyde into aldol dehydration tower, dehydrating 3-hydroxybutyraldehyde at dehydration tower top temperature of 106-118 degrees C, bottom temperature of 139-141 degrees C and tower pressure of 0.25 MPa, condensing tower top distillation product, passing tower top distillation product condensate and uncondensed gas into primary distillation tower for concentration, obtaining distilled acetaldehyde gas condensate, recycling acetaldehyde gas condensate to condensation tower, recovering crotonaldehyde at tower packing segment, obtaining crude crotonaldehyde with 89% purity, refining to obtain 99.3% pure refined crotonaldehyde, and introducing dehydration tower bottoms and initial boiling wastewater directly into incinerator to achieve zero discharge of wastewater.