To avoid the circularly shift range on multi-range hydro-mechanical continuously variable transmission（HMCVT）,taking the multi-range hydro-mechanical CVT of the wheel tractor of YTO-400 as example,the transmission characteristic of multi-range hydro-mechanical CVT is analyzed.The causes of the circularly shift range are researched,and eliminating mechanism is presented.The effectiveness of principle of averting the circularly shift range is simulated by using the theory of Finite State Machine,which employs the actual and theoretical displacement ratio,output speeds of multi-range hydro-mechanical CVT as the control parameter.The research results indicate that,the volumetric efficiency of the pump-motor system is the important reason for the factor of efficiency difference of the circularly shift range.By controlling the increase of the theory displacement ratio of the multi-range hydro-mechanical CVT,the actual displacement ratio is maintained at the same time,which effectively avoids the cycle change of the multi-range hydro-mechanical CVT.A theoretical foundation for the development of multi-range hydro-mechanical CVT control system is provided.