The invention discloses a cosynthesis device and method of hexanol, cyclohexanone and adipic acid in microchannels. The method comprises the steps of mixing and preheating cyclohexane and oxygen or air by a gas-liquid micro mixer, entering a micro reaction tube in an air thermostat, and reacting, wherein the cyclohexane flow is controlled by a laminar flow pump, the oxygen or air flow is controlled by a mass flow controller, the cyclohexane flow and the oxygen or air flow are kept at a certain ratio, and the reaction pressure is controlled by a back pressure valve; and separating the reaction product by a gas-liquid micro separator, collecting the liquid-phase product by a storage tank, and discharging the gas phase. According to the invention, continuous production of cyclohexanol, cyclohexanone and adipic acid is realized; because the gas-liquid micro mixer, the micro reaction tube, and the gas-liquid micro separator are adopted, the specific surface area of the fluid passing through the channels is large, heat transfer effect of mixing, reaction, separation and other processes is good, pure oxygen and air can be used as an oxidant in the reaction, operation can be carried out at higher reaction pressure and reaction temperature, the reaction safety is greatly improved, and the selectivity and conversion rate are greatly improved.