The reversing mechanism is the key of reversal plough. In order to achieve the aim of convenient and smooth exchanging direction, this paper analyzed the reversing mechanism of reversal plough, deduced the relationship among parameter h, angle BAD and foundation girder's angle acceleration and the force of cylinder. The mathematic model of reversing mechanism was developed and C language was used to optimize the parameters. The design result was used to optimize 1LB-240 plough. The check and test show that the result of design is reasonable and exchanging direction is convenient and smooth. This method can be used to optimize the design of similar mechanisms.