A modular oven structure comprising a frame and an air channel structure, wherein, a tunnel air inlet chamber, a tunnel air return chamber, and a tunnel drying chamber between the tunnel air inlet chamber and the tunnel air return chamber, are arranged in the frame; a tunnel air inlet plate is arranged between the tunnel air inlet chamber and the tunnel drying chamber, and a tunnel air return plate is arranged between the tunnel air return chamber and the tunnel drying chamber; a plurality of apertures are arranged both in the tunnel air inlet plate and in the tunnel air return plate; a fan air inlet chamber is arranged above the tunnel drying chamber, and a heater is arranged in the fan air inlet chamber; a fan air outlet chamber is arranged between the fan air inlet chamber and the top of the frame; a circulation fan is arranged at the top of the frame, and an air inlet of the circulation fan is in communication with the top of the fan air inlet chamber; wherein the modular oven structure further comprises a temperature control system and a control device, wherein the temperature control system comprises several temperature sensors, and the temperature sensors are arranged in the tunnel air inlet chamber and/or the tunnel air return chamber and/or the tunnel drying chamber; and output ends of the temperature sensors are connected to the control device, and an output end of the control device is connected to a control signal input end of the heater and a control signal input end of the circulation fan, characterised in that the distribution density of apertures in the upper portion of the tunnel air inlet plate is higher than the distribution density of apertures in the lower portion of the tunnel air inlet plate, and the distribution density of apertures in the upper portion of the tunnel air return plate is lower than the distribution density of apertures in the lower portion of the tunnel air return plate. a tunnel air inlet chamber, a tunnel air return chamber, and a tunnel drying chamber between the tunnel air inlet chamber and the tunnel air return chamber, are arranged in the frame; a tunnel air inlet plate is arranged between the tunnel air inlet chamber and the tunnel drying chamber, and a tunnel air return plate is arranged between the tunnel air return chamber and the tunnel drying chamber; a plurality of apertures are arranged both in the tunnel air inlet plate and in the tunnel air return plate; a fan air inlet chamber is arranged above the tunnel drying chamber, and a heater is arranged in the fan air inlet chamber; a fan air outlet chamber is arranged between the fan air inlet chamber and the top of the frame; a circulation fan is arranged at the top of the frame, and an air inlet of the circulation fan is in communication with the top of the fan air inlet chamber; wherein the modular oven structure further comprises a temperature control system and a control device, wherein the temperature control system comprises several temperature sensors, and the temperature sensors are arranged in the tunnel air inlet chamber and/or the tunnel air return chamber and/or the tunnel drying chamber; and output ends of the temperature sensors are connected to the control device, and an output end of the control device is connected to a control signal input end of the heater and a control signal input end of the circulation fan, characterised in that the distribution density of apertures in the upper portion of the tunnel air inlet plate is higher than the distribution density of apertures in the lower portion of the tunnel air inlet plate, and the distribution density of apertures in the upper portion of the tunnel air return plate is lower than the distribution density of apertures in the lower portion of the tunnel air return plate.