For lithium secondary microbattery anode, the tin oxide thin films with the various Si additions (0, 2, 6, 10, 20mol%) were prepared on the p-type (100) SiO2/Si substrate by R.F. magnetron sputtering method at the substrate temperature of 300°C under the gas ratio of Ar/O2 (7/3). The effect of Si addition to the SnO2 thin film on the structural change and electrochemical performance and the reversible capacity performance was investigated. As Si addition amounts increased, Si-O bonding density increased and Sn-O bonding density decreased. The addition of optimum Si amount led decrease of Sn oxidation state so that the irreversible capacity was reduced and cycle characteristic was enhanced during the charge-discharge test. SnO2 films with 6mol%Si had the highest reversible capacity of 700mAh/g after 100cycles.