We propose a new scheme for molecular mirror with a blue-detuned surface plasmon ploariton field excited on a microstructural metal film and study the dynamic process of reflection of cold molecules by Monte Carlo simulation. Our study shows that this mirror can realize a reflection of cold iodine molecular beam with a longitudinal temperature of 10 mK and a transverse temperature of 1 mK with a reflectivity of 55.89% when the incident laser is of a 10 ns pulse width and its intensity is I0=1.0 109 W/cm2; and the molecular reflectivity increases with increasing incident laser intensity.