<p>Interior permanent magnet synchronous motors (IPMSMs) are widely used in electric vehicles due to high power density. The operating efficiency and overall performance under diverse driving conditions directly affect vehicle range and service life. To address the complexity of real driving conditions, the challenge of balancing multiple performance metrics at a single operating point, and the high dimensionality of conventional multi-objective optimization, this article proposes a novel delta-type rotor structure and a high-efficiency dimension-reduced multi-objective optimization method for the full operating domain, aiming to improve motor efficiency and achieve efficient design. The proposed rotor employs segmented magnetization of permanent magnets together with auxiliary magnetic isolation slots, which effectively suppress rotor magnetomotive-force (MMF) harmonics and reduce iron losses, thereby improving motor efficiency. To increase optimization efficiency, representative operating points and corresponding energy weights are extracted from the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) driving cycle using a clustering method. A combined sensitivity analysis and principal component analysis (PCA) is then applied to reduce the dimensionality of the design parameters and optimization objectives. Within the reduced-dimension design space, the Nondominated Sorting Genetic Algorithm II (NSGA-II) is utilized to perform optimization and verification. The results show that the proposed rotor structure significantly reduces iron losses, increases peak efficiency, and broadens the high-efficiency operating region, while effectively mitigating torque ripple and electromagnetic vibration. In addition, the dimension-reduction process greatly simplifies optimization dimensionality and substantially improves overall design efficiency.</p>