This paper demonstrated acylation of cellulose with long chain fatty acid and internally plasticized cellulose films obtained by casting. The degrees of substitution (DS) and molar yields of fatty acid, Ts-Cl amounts and reaction time, and as well as the property of final products were studied. Partially derivative celluloses presented glass transition compared to starting cellulose. However, thermal behaviors of the internally plasticized esters with different DS were similar. Dynamic mechanical thermal analysis (DMTA) in tension mode revealed separate relaxations, denoted α and β, corresponding to the glass transition and side-chain melting processes, respectively. According to this, these longer chain esters (LCCEs) showed promise as internally plasticized cellulose films because the supermolecular structure of cellulose was significantly changed with the introduction of longer substituent.