Robots　with　intelligent　moving　and　manipulating　ability　are　able　to　improve　productivity　of　agriculture　work.　We　prototyped　a　mobile　robot　equipped　with　reductant　manipulator　(7-DOF).　Here,　for　controlling　the　manipulator　precisely,　we　investigate　the　inverse　kinematics　(IK)　issue　of　the　manipulator.　A　novel　IK　solving　method　by　adopting　an　improved　differential　evolution　algorithm　has　been　validated.　Also,　random　change　crossover　is　employed　to　restrict　the　tendency　of　falling　into　local　optimization　when　we　use　the　algorithm.　In　parallel,　considering　the　position　and　posture　errors,　boundary　processing　has　been　redesigned　for　avoiding　joint　limits.　Thereafter,　we　obtain　the　global　optimal　IK　solutions.　Simulation　tests　have　been　carried　out　using　the　numerical　model　of　the　redundant　arm.　By　testing　accuracy　and　stability　of　the　arm,　we　verify　the　feasibility　and　efficiency　of　the　proposed　approach.