In view of the problem that the driver frequently turns round to observe and manually operate the baler during the process of straw-bundling and bale-unloading of minitype round baler, an automatic manipulation and alarming device was developed. The device mainly consisted of three travel switches as a singlechip, an operation mechanism driven by electric cylinder and a buzzer. By analyzing the working process of straw-bundling and bale-unloading, three travel switches were used to detect whether straw was filled with bale chamber, straw-bundling motion finished and the bale fell to the ground from bale chamber. The control flow of straw-bundling and bale-unloading was designed, and the control parameters of straw-bundling time and bale-unloading time were determined. Simulation tests of indoor working condition showed that the single chip could process the trigger signal of three travel switches to make electric cylinder stretch out and draw back, and the hydraulic valve handle was driven by the operation mechanism to realize automatic bale-unloading. The buzzer made different rhythm of the alarm sound during the process of straw-bundling and bale-unloading to effectively detect spurious triggering of travel switches and parts fault, which improved the reliability of the system. The pick-up and baling tests of prototype baler showed that the device may improve the working efficiency of minitype round baler by 22.5% to 32.2%, and the success rate of straw-bundling and bale-unloading may reach 100%.