As urban development shifts to the stage of stock improvement and quality enhancement， optimizing the scale structure of “production-living-ecological” space has become a core issue for high-quality development. This study constructs a theoretical analytical framework of “ecological scale constraint - functional proportional adaptation - internal structure coordination” and reveals the underlying contradictions in China’s urban spatial structure based on multi-source spatial data. The results show that the main contradiction of “production-living-ecological” space in Chinese cities has shifted comprehensively from total scale shortage to structural proportional imbalance. Although ecological space maintains the bottom line of scale control， its overall quality remains low. At the macro level， construction space exhibits imbalanced supporting space and a differentiated production-residence structure； at the micro level， it falls into internal structural mismatch and a disconnection between service supply and demand at the micro level. Accordingly， a progressive optimization paradigm of “locking scale boundaries - correcting macro proportions - restructuring internal structure” is proposed. Furthermore， from the perspective of precise governance， it is suggested to accelerate the standard transformation of key structural indicators and the construction of a quantitative support foundation， so as to provide a scientific basis for promoting the transformation of spatial governance from empirical judgment to precise quantification.