A T-Na nanocompound gel was prepared with tris (chlorisopropyl) phosphate (TCPP) and sodium montmorillonite (NaMMT). The effects of TCPP/NaMMT mass ratios, moisture content and temperature on the gelation were investigated. The stability and nano-structure of nanocompound gel were characterized by X-ray diffraction, thermogravimetric analysis and transmission electron microscopy (TEM). The adsorption of T-Na nanocompound gel on organic solvents such as toluene was analyzed. The dispersion of layered NaMMT in TPU/T-Na composites was determined by TEM. The flame retardant effect of T-Na nanocompound flame retardant on thermoplastic polyurethane (TPU) was investigated by a cone calorimeter (CONE). The results show that the stable nanocompound gel is formed and the interlayer spacing of NaMMT increases from 0.98 nm to 3.15 nm when the mass ratio (TCPP/NaMMT) ranges from 2:1 to 7:1. The presence of moisture and the higher temperature can accelerate the gelation of T-Na nanocompound. In the T-Na gel, there exists a strong interaction between TCPP and NaMMT as the mass ratio is 1:5.5-5.7. T-Na nanocompound gel is capable of adsorbing large amounts of toluene. In the TPU/T-Na composites, NaMMT is a nano-dispersion material with intercalated and exfoliated state. According to the results by CONE, T-Na nanocompound flame retardant is more effective for TPU rather than relatively pure NaMMT and TCPP.