The invention provides a 3D color printer capable of monitoring product quality online. The 3D color printer comprises a base, a vertical column, a printing nozzle, a printing moving mechanism, a workbench, a scanning device and a control processor, wherein the printing moving mechanism is connected with the printing nozzle and used for driving the printing nozzle to move within an XY plane; the workbench is arranged below the printing nozzle; a first driving mechanism is connected with the workbench and drives the workbench to move in the Z axis direction; an annular chute is arranged on the base; the projection, on the base, of the workbench is within an area defined by the inner contour of the annular chute; the scanning device is mounted on the chute; a second driving mechanism is in transmission connection with the scanning device and drives the scanning device to slide along the chute; the printing nozzle comprises a base plate, a stirring box, a stirring device, a heating block, a conveying tube, an extruding tube, a temperature sensor, an assistant heating layer, a heat preserving layer, a temperature controller, a branched air tube, an annular air tube and an air pump. With the adoption of the 3D color printer, a color model can be printed, and the accuracy is high; meanwhile, the model quality and color quality of a printed object can be monitored.