Abstract: In order to meet the requirements of the ideal kinematics characteristic, a new non-circular gear-crank slider hay baler mechanism was proposed, the ideal kinematics characteristic of the hay baler was analyzed, and the equation of ideal speed curve was built in this paper. The dynamics model of this new mechanism was built to carry out the reverse design of the pitch curve of non-circular gear that could meet the working requirements for the purpose of getting the ideal speed curve. Compared with the traditional slider crank baler mechanism, through example calculation, compression time of the new mechanism increased by 30% in one working cycle, the new mechanism could compress rapidly in small resistance stage while at a constant low-speed in big resistance stage, and the maximum input power decreased by 28.6%.