A　complex-shaped　underwater　robot　with　a　device　which　can　weld　for　a　nuclear　reactor　pool　in　emergency　and　inspect　in　daily　was　developed.　Hydrodynamic　coefficients　in　the　dynamic　model　were　critical　to　control　precisely.　In　this　work,　a　numerical　simulation　of　robot　had　been　employed　for　hydrodynamic　coefficients　calculation　based　on　the　computational　fluid　dynamics　(CFD).　Hydrodynamic　coefficients　including　inertial　hydrodynamic　coefficients,　viscous　hydrodynamic　coefficients　were　respectively　solved　by　simulating　virtually　a　steady-state　motion　simulation　test　and　an　unsteady-state　motion　simulation　test　in　CFD.　A　prototype　test　in　a　circulating　water　channel　had　been　launched　to　validate　simulation　results.　Furthermore,　viscous　hydrodynamic　and　inertia　hydrodynamic　coefficients　were　acquired.　The　accuracy　and　reliability　of　hydrodynamic　coefficients　was　proved　by　comparing　to　the　prototype　test　results.　All　work　carried　out　was　indicated　to　be　benefit　to　hydrodynamic　coefficient　study　and　complex-shaped　underwater　robot　control.