Porous polymer-nanocrystals (NCs) organic-inorganic nanocomposites with integrated functions, enhanced stability, and controlled morphology are highly demanded across various fields due to their unique physicochemical properties. Herein, uniform macroporous polystyrene (MPS) microspheres loaded with various functional NCs were designed and synthesized through a facile and controllable impregnation method, enabling the applications of nanocrystals in solutions and their convenient recycling and recovery. As a typical example, Ag-loaded MPS composite (denoted as Ag@MPS) microspheres are synthesized and they exhibit uniform spherical morphology, good dispersion, and an interconnected macroporous structure. Benefiting from these distinctive structural features, Ag@MPS microspheres demonstrate exceptional catalytic performance in the reduction of 4-nitrophenol, achieving a fast reaction rate constant of 0.394 min⁻¹ at room temperature. Moreover, owing to the highly accessible Ag NCs in the macroporous polystyrene (PS) matrix, the Ag@MPS microspheres display superior antibacterial activity, with antibacterial rates of 93% against Gram-positive bacteria and 99% against Gram-negative bacteria.