2D lamellar aluminophosphate (LAP) is successfully exfoliated into nanolayers in polyurethane (PU) through the combination of organically modification and solution casting method. Morphological studies by XRD and TEM show that the exfoliated LAP nanolayers are dispersed well in the PU matrix. The introduction of small amounts of LAP nanolayers (<= 5.0 wt %) results in obvious enhancements in the thermal properties and mechanical performance of PU/LAP nanocomposites. These enhancements are benefiting from the good dispersion and exfoliated morphology of stiff LAP nanolayers and strong interfacial interaction between LAP nanolayers and the matrix. LOI and MCC results indicate that the LAP nanolayers incorporated also improve the flame retardancy of nanocomposites. Detailed flame-retardant mechanism is proposed. Physical barrier effect of LAP nanolayers and the graphitized char formation catalyzed by LAP play key roles in the flame retardancy enhancement.