Development of a facile and cost-effective surface-enhanced Raman scattering (SERS) sensor with high sensitivity for the on-site rapid detection of trace molecules is a compelling need. Here we report how a capillary-based three-dimensional network porous silica material decorated with gold nanoparticles (3D-PSM@AuNPs) serves as an ideal platform for the rapid static liquidphase detection of trace molecules. The SERS sensor is prepared by an in situ polymerization method to form a 3D continuous interconnected porous network in an ultraviolet transparent quartz capillary with a facile fabrication process. The unique porous network of the silica, which could provide a high specific surface area in a focus volume, endows the resultant material with a high density of SERS enhancement sites and a "hot-spot", which has precisely guaranteed the detection sensitivity. More importantly, the unique structure of the capillary could also present an aid to reduce the energy loss of the laser via multiple reflections and thus effectively improve the utilization rate of the laser beam. Using 4-mercaptopyridine (4-MPY) in aqueous solution as a model molecule, the porous silica material exhibits a high detection sensitivity (10 −11 M), excellent stability, and repeatability. Moreover, the obtained 3D-PSM@AuNP sensor is applied for the analysis of phosmet residues on orange peel and vegetables. The results demonstrate that this 3D-PSM@AuNP sensor can successfully realize Raman reporter-free and rapid on-site detection of trace molecules in liquids, which provides a promising platform in various fields of micro-volume liquid sample analysis, especially in liquid biopsy analysis.