A practical approach to designing 3D porous materials with new functionalities for oil spill clean‐up attracts widespread attention. The carbonized seaweed‐coated melamine sponge (CMS) can selectively absorb oil immediately due to its countless pores using capillary‐driven force to absorb oil. The microstructure and behaviors of the CMS are thoroughly investigated in relation to the unique porous structure, mechanical stability, wetting response, and in‐depth processing of the high‐speed visualization experiment to determine its promising abilities. For the special CMS structure with a unit cell size of 1 × 1 × 1 cm, the total volume of oil inside the capillary tube is drawn inward after 56 ms, and the absorption rate is estimated to be ≈15 200 liters per spare metre hour without any external power inputs. According to the results, theoretical models are proposed to estimate the oil absorption rate as a function of time by continuity of the oil column in the capillary tube based on quantitative analysis of the optically analyzed oil interface phenomena. It is first shown to be a reliable approach for describing volumetric absorption rate and effective CMS thickness by visualizing the capillary spreading flow. It is expected that this research will hold tremendous potential strategies for environmental remediation.