The present invention provides an intelligent extruding and blow molding product wall width control system, including an ultrasonic on-line inspecting of the wall width of the product inside a mold module, an industrial-control and disposal module and a mold opening-gap control module. The ultrasonic on-line inspecting of the wall width of the product inside a mold module is connected with the industrial-control and disposal module; the industrial-control and disposal module is connected with the mold opening-gap control module. An intelligent extruding and blow molding product wall width control method mainly includes the operation steps of automatically obtaining a gap curve of an initial machine, ultrasonic on-line inspecting of the wall width of the product inside a mold, real time controlling the wall width of the product of blowing molding etc. The present invention can realize the on-line and real time control towards the wall width of the blow molding product and accordingly to improve the performance of the blown molded product and reduce the cost of the material and the production cost.