The work aims to study the measurement feasibility of automatic measurement setup in the process of online extrusion compression molding of packaging boxes with highly filled wood plastic composite as well as the factors influencing the accuracy. The composites made of different materials were evaluated at different extruder speeds and melt temperatures by the self-made online extrusion measurement setup for the automatic wood plastic packaging composites, and the measurement error was calculated. With the increase of plant fiber content in the wood plastic packaging composites, the measurement stability became poor and the measurement accuracy decreased. Under the same formula, the best extrusion speed of the extruder was 200 r/min. When the melt temperature was 190 ℃, the measurement effect was the best. It is feasible to measure the highly filled wood plastic packaging composites with the self-made online extrusion measurement setup. The formula, extruder speed and processing temperature of the composites will directly and indirectly affect the measurement accuracy. By changing the technological parameters of specific formula, the best measurement accuracy can be obtained.