ABSTRACT : For lithium secondary microbattery anode, the tin oxide thin films with Si addition (0, 2, 6, 10, 20 mol%) were prepared with R.F. magnetron sputtering at substrate temperature of 300oC and Ar : O2=7 : 3 atmosphere. As Si addition amount increased, Si-O bonding density increased and Sn-O bonding density decreased. The addition of optimum Si amount led the decrease of Sn oxidation state so that the irreversible capacity reduced and cycle characteristic enhanced during charge-discharge test. SnO2 films with 6 mol% Si had the highest reversible capacity of 700 mAh/g after 100 cycles.