The APDL language was used to obtain the parameter model of tri-directional beam string structure (TBSS) of new Guangzhou Railway Station. Then design optimization was conducted for the effective cross-sections and geometry parameters of TBSS with the first-order method. And when the rise and sag were fixed, the proper structural cross-section was also discussed with graded and integrated optimization method respectively. The results show that the rise and sag are very important design parameters of TBSS. The optimum rise of upper arch of TBSS for new Guangzhou Railway Station is 9.189 m; the sag to span ratio of cable is not less than 0.034; the economical rise to sag ratio is about 0.22~0.23. It can also be found that the weight ratio of upper arch elements to the whole structure is large, so the amount of steel can be reduced by decreasing the thickness of upper arches. And the optimum rigidity ratio of beam to cable of TBSS of new Guangzhou Railway Station is 1.23×10-4 by integrated optimization.