To integrate large-scale renewable resources efficiently and flexibly, the concept of multi-terminal high voltage direct current (MT-HVDC) transmission grid was proposed for the regions were rich in renewable energy resources. In this paper, an optimal capacity planning model of converter stations was proposed to maximize the collected and transmitted renewable energies for the MT-HVDC system. The proposed model was a quadratic programming model and the global optimization results can be obtained by the standard solver for quadratic programming. The total capacity constraint of the MTHVDC, the capacity constraint of the sending-end transmission channel, and power flow constraints within the MT-HVDC were also considered in the propose model. The case studies with different scenarios were carried out and discussed. The calculation results demonstrated that the optimized capacities of the converter stations for the MT-HVDC can be determined with the historical operation data.