In this work, layered metal phenylphosphonates are synthesized via hydrothermal method and their morphology is observed by scanning electron microscopy and transmission electron microscopy. Then, their polystyrene (PS) composites with 2 wt % phenylphosphonates are fabricated and thermal stability as well as combustion behavior are investigated. Excellent dispersion state of fillers and strong interfacial interaction between PS and phenylphosphonates are achieved. Char residue yield of the PS composites is enhanced in TGA test and the values of peak heat release rate are decreased appreciably, suggesting the improvements in thermal stability and flame retardancy. Moreover, the amount of aromatic compounds released from PS is decreased remarkably after the incorporation of phenylphosphonates.