A new route to synthesizing acrylic acid from acetic acid and formalin by one-step aldol condensation reaction was proposed and developed. V-P/SiO2 oxide bifunctional catalysts were designed and prepared by ultrasonic impregnation method. The catalysts were characterized by XRD, BET, TEM, TG/DTA, and XPS, as well as NH3- and CO2-TPD and pyridine-FTIR methods. Catalytic performance wag evaluated using a fixed-bed tubular microreactor operating with a CH3COOH/HCHO (HAc/FA) molar ratio of 10 under atmospheric pressure. Influences of the balance between acidic and alkaline sites, as well as ratio of V4+ and V5+, on catalyst activity were further studied. Reaction parameters were systemically optimized. Through a series of comparisons, V-P/SiO2 binary oxide catalyst with a bulk density ratio of 1:2 was selected.