The adsorption and decomposition of trimethylene oxide (C 3 H 6 O) molecule on the Al(111) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell (6 × 6 × 3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between C 3 H 6 O molecule and Al atoms induce the C-O bond breaking of the ring C 3 H 6 O molecule. Subsequently, the dissociated radical fragments of C 2 H 6 O molecule oxidize the Al surface. The largest adsorption energy is about −260.0 kJ/mol in V3, V4 and P2, resulting a ring break at the C-O bond. We also investigated the decomposition mechanism of C 3 H 6 O molecules on the Al(111) surface. The activation energies (E a ) for the dissociations V3, V4 and P2 are 133.3, 166.8 and 174.0 kJ/mol, respectively. The hcp site is the most reactive position for C 3 H 6 O decomposing.