Al thin films were synthesized on TiN/Si substrate by MOCVD using N-methylpyrrolidine alane (MPA) precursor. Effects of substrate temperature, reaction pressure on the deposition rate, surface roughness and electrical resistivity were investigated. The early stage of Al thin film formation was analyzed by in-situ surface reflectivity measurement with a laser and photometer apparatus. From the Arrhenius plot of deposition rate vs. substrate temperature, it was found that the activation energy of surface reaction was 91.1kJ/mole, and the transition temperature from surface-reaction-limited region to mass-transfer-limited region was about $150^{circ}C$. The growth rate increased with the reaction pressure, and average growth rates of $200{sim}1,200nm/min$ were observed at various experimental conditions. Surface roughness of the film increased with the film thickness. The electrical resistivity of Al film was about $4{mu}{Omega}{cdot}cm$ in the case of optimum condition, and it was close to the value of the bulk Al, $2.7{mu}{Omega}{cdot}cm$.