Battery thermal management system is critical to ensure the temperature of the battery pack in electric vehicles within a suitable range. In this study, the battery pack is cooled by the parallel mini-channel cold plate (PMCP). The performance of the PMCPs with I-type (PMCP I), Z-type (PMCP Z), and U-type flows (PMCP U) are studied using numerical method. Then, the edge width and convergence channel width of the three systems are designed. The cooling performance of the PMCPs is effectively improved after the structure design. Subsequently, the symmetrical system is constructed based on each PMCP. The numerical results show that the symmetrical systems achieve lower maximum temperature, smaller maximum temperature difference, and lower energy consumption. Among the three systems, the performance of the symmetrical PMCPs I and Z is similar and better than that of the symmetrical PMCP U. Finally, the dimensionless analysis is performed to explore the influences of various parameters on the final designed cold plate. The results indicate that the inlet cooling water temperature and heat flux density applied to the cold plate do not affect the structure of the final designed system. Moreover, the designed systems have good performance under different mass flow rates. Highlights PMCPs with different flow patterns are applied in BTMS. Performance of PMCPs is improved through multi-parameter structure design. The symmetrical systems are constructed for performance improvement. T-0 and q(0) do not affect the structure of the designed PMCP. Delta T-max and W-P of designed PMCP are respectively reduced by at least 19% and 61%.