A net self-wrapping mechanism for round baler was designed. The cam was used as transmission and control mechanism. The oscillating linkage was used as cam follower. The traction unit, wrapping unit and cutting unit were controlled for wrapping, recording and cutting. The wrapping performance experiment showed that this device could wrap dry bales of 80～120 cm width and silage round bales of 80～100 cm width. The most cost-effective operation was wrapping dry bale of 1.2 m width in three laps or wrapping silage round bale of 1.0 m width in four laps. 