Abstract: Wearable devices with excellent moisture permeability and waterproof performance can prevent water vapor accumulation on the skin surface while resisting external contaminated liquids, providing a safe and comfortable long-term wearing experience. However, porous membranes prepared by traditional solid template methods are difficult to form interconnected pore structures, which seriously hinders the transmission of water vapor and limits their practical applications as wearable devices. A method is presented in this paper for preparing polydimethylsiloxane (PDMS) porous membranes with high-efficiency moisture-permeable, waterproof, and radiative cooling properties by using a sucrose-invert syrup complex as sacrificial template. Benefiting from the composite template with an interconnected structure, the prepared porous membrane has a high porosity and a "window" structure between pores that facilitates the rapid passage of water vapor and greatly increases water vapor transmission rate (WVTR). The WVTR of the porous membrane reaches 2666 g∙m⁻²∙d⁻¹ at a thickness of 2 mm, which is far superior to the PDMS porous membrane prepared by conventional solid templates. The microsized "window" structure and superhydrophobic modified surface effectively prevent the penetration of liquid water, enabling the good waterproof performance of the membrane while ensuring high water vapor transmission rate. Meanwhile, the study indicates that the PDMS porous membrane has excellent radiation cooling characteristic due to the strong mid-infrared emissivity and high solar reflectivity, which results in an average subambient cooling effect of 5.8℃ in hot environment. Additionally, the PDMS porous membrane exhibits good strength and wear resistance, it maintains its superhydrophobicity even after 200 cycle of bending or 50 cycles of sandpaper abrasion. The porous PDMS membrane reported in this study provides a wide range of potential applications in flexible electronics and smart wearable technology.