The Yangtze River Delta (YRD) is the most developed area in China attracting global attention. Noting that the concentration ratio (CR(n)), Herfindahl-Hirschman Index (HHI) (also including Gini coefficient and Aitchison distance) and shift-share analysis (SSA) are only allowed to describe the concentration, inequality and competition of a multi-port system respectively. A novel ternary diagram method is proposed to include these five methods together and provide a comprehensive and visual tool to conveniently investigate the concentration gradient, inequality and competition of the YRD multi-port system simultaneously. The ternary diagram also permit to substitute individually for the CR(n), HHI (also including Gini coefficient and Aitchison distance) and SSA as a tool to investigate the concentration, inequality and competition of a multi-port system. This method provides a new perspective for better interpretation of the spatial and temporal evolution of shipping and multi-port systems.