以聚甲基丙烯酸甲酯（PMMA）为高分子聚合物基体，以非晶二氧化硅（SiO2）为填料，采用静电纺丝法制备具有日间辐射制冷功能的复合纤维，并采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、紫外-可见-近红外（UV-Vis-NIR）分光光度计、傅里叶红外光谱仪（FT-IR）等对复合纤维的形貌、结构和光学性质进行表征。结果表明：静电纺丝制得的复合纤维直径约为800nm；纯PMMA纤维的禁带宽度为4.95eV，不吸收可见光，且纺丝过程中的取向结晶导致纤维内部存在晶区和非晶区，对可见光不透过而呈现白色，因而使纤维的200~2500nm短波段反射率高达97.57％；经静电纺丝后，适量的纳米SiO2粉体颗粒分散在复合纤维中，可大幅提高复合纤维的发射率；当SiO2的掺量为7.5％（质量分数，余同）时，复合纤维在太阳200~2500nm短波段的反射率和8~13μm大气窗口的发射率分别高达96.53％和0.903。文中还采用自制装置测试了纤维在实际环境下的降温效果，结果表明，复合纤维具有良好的降温效果，其日间背面温度低于环境温度2~4℃。文中提出的无机粉体与有机物复合的纤维制备模式为辐射制冷材料的实际应用提供了新的方案。

By Using polymethyl methacrylate （PMMA） as the high-molecular polymer substrate and SiO2 as the filler，a kind of composite fiber with daytime radiative cooling function was prepared via electrospinning.Then，the XRD，SEM，TEM，UV-Vis-NIR and FT-IR were used to characterize the morphology，structure and optical properties of the composite fiber.The results show that the diameter of the electrospun composite fiber is about 800nm in diameter.The forbidden band width of pure PMMA fiber is 4.95eV，which makes the fiber do not absorb visible light; and the orientation crystallization in the electrospinning process leads to crystalline region and amorphous region in the fiber，which does not transmit visible light and displays white，thus obtaining a 200~2500nm short-wavelength reflectivity as high as 97.57%.After the electrospinning，nano-SiO2 powder particles with appropriate amount are dispersed in the composite fiber，which can greatly improve the emissivity.When the doping amount of SiO2 is 7.5%，the reflectivity of the composite fiber in the solar short-wavelength band of 200~2500nm and the emissivity of the 8~13μm atmospheric window are respectively up to 96.53% and 0.903.By using a self-made device to test the cooling effect in the actual environment，it is found that the composite fiber behaves good cooling effect，the temperature of the back of the composite fiber in the daytime is lower than the ambient temperature by 2~4℃.The proposed preparation method of composite fiber with inorganic powder and organic matrix provides a new solution to the practical application of radiative cooling.