The modification principle and method of teeth profiles of ring gear have been put forward for eccentric wheel handspike planetary transmission.The modification incremental functions of teeth profiles for middle part,tip part and root part have been established,and it has been proved that teeth profiles modified is sequential and slippery.The formulae of meshing movable teeth number after modification have been founded.The methods and steps for confirming teeth profiles modification basic parameter have been discussed.The example of teeth profiles modification has been put forward for eccentri...