<p>Crude oil has long been the “black gold” of the global economy, and its fractionation relies on thermal distillation, a highly energy-intensive process. In contrast, crude oil fractionation <i>via</i> membrane separation can operate under mild conditions, avoiding phase transitions, and thereby substantially reducing the energy consumption associated with thermal separation processes. Numerous microporous polymer membranes have been developed to target the fractionation of oil mixtures through precise molecular design and structural modulation for the selective separation of hydrocarbon compounds. However, the intrinsic trade-off between permeance and selectivity remains a core bottleneck limiting their advancement. Herein, we summarize the synthetic strategies for microporous polymer membranes, focusing on tailored pore structures, anti-swelling capabilities, and selective transport of hydrocarbon compounds across these membranes. The performance of representative materials for practical crude oil fractionation was also highlighted. We also outline critical unresolved challenges, including cost-efficient large-scale fabrication, long-term stability under harsh crude oil environments, and further optimization of the permeance-selectivity balance, issues that must be addressed to promote the deployment of microporous polymer membranes.</p>