In this article, silver nanoparticles (AgNPs) modified nanofibers that represent a novel kind of packing materials for micro-solid phase extraction (mu-SPE) is reported for the first time. The composite material was fabricated through in-situ formation of AgNPs on the polydopamine (PDA) coated polystyrene electrospun fibers (PS@PDA-Ag). The nanofibers displayed desirable hydrophilicity, large surface area, high porosity, good extraction ability and certain capacity to resist matrix interference. A mu-SPE combined with liquid chromatography-mass spectrometry (LC-MS) method was developed for the online determination of three monohydroxy polycyclic aromatic hydrocarbons (OH-PAHs) metabolites in human urine. Under the optimal conditions, good linearity (0.02-5 ng mL(-1)) was acquired with the correlation coefficients (R-2) being larger than 0.9962. Low limits of detection (0.007-0.032 ng mL(-1)) expressed the satisfactory sensitivity of the method. Moreover, the intraday relative standard deviation values lower than 9.7% and the recoveries among the range of 71-116% were obtained. In general, the online mu-SPE-LC-MS method had the features of simplicity, rapidity, sensitivity and automation, and it was expected to become a promising approach for the online analysis of trace OH-PAHs in complex biological samples. (C) 2017 Elsevier B.V. All rights reserved.