The present invention discloses a grass cutting machine. It includes a grass cutting machine main body, a lower operation bar extended towards rear portion from said grass cutting machine main body and an upper operation bar connected with the lower operation bar. The described lower operation bar and upper operation bar have a connection portion, the described connection portion is equipped witha turning shaft and an engaging mechanism. Said engaging mechanism has engaging point on the curved surface using said turning shaft as centre of cycle. The described engaging mechanism can be selectively engaged on the engaging point or unengaged. When the engaging mechanism is unengaged, the upper operation bar and lower operation bar can be folded, and when the engaging mechanism is engaged, the operation handle can be regulated to the different positions.