Operational efficiency and working quality of silage round baler were mainly determined by the compression chamber. For the feeding difficulties of traditional compression chamber, a new type of round bale device with logarithmic spiral geometric features was designed for the silage job. This device consists of a preload feeding mechanism and the logarithmic spiral type secondary extrusion mechanism. The pressure angles of this machine were experimented with different moisture contents of corn stalks. Results of field test indicate that, plugging problems were solved by using logarithmic spiral geometry chamber baler compared with the circular cavity compression chamber balers. The pressure angle of logarithmic spiral baler feeder must be less than 20° under the feeding process of thick, hard and moist materials. Under the conditions that the pressure angle of 15° and the moisture content of 50%～70%, the feeding speed could match the baling speed in higher efficiency. To form bales of equivalent mass, the device had good adaptability for high moisture corn stalks. The design principles and experimental results of logarithmic spriral compression chamber provided an optimization direction for improving the working efficiency of silage round baler.