On the basis of the modeling and analyzing of the transmission system of the PQS-3-D elevator for car in the preamble,this article analysis the reason of the small difference of the angular speed,angular acceleration,angular displacement curve between the bilateral symmetry components.Actually,it is the result of that the torsional rigidity of the bilateral drive shafts are different,therefore has made the revision suggestion to the drive shaft parameter.And analysis the output curve after improving,and in the same time,the difference in the corresponding angular speed,angular acceleration,angular displacement curve of the bilateral symmetry components will obviously decrease.