Single walled-carbon nanotube (SWCNT) thin film is one of the candidates for the next-generation flexible and transparent conductive thin film, which is a crucial component in various applications such as electrodes of flat-panel displays, solar cells, light emitting diodes, and touch panels. An intensive research work is underway to develop thin and flexible SWCNT films. The most important requirement of an SWCNT thin film is that it should show a low sheet resistance coupled with a high transparency. In this work, thin films of SWCNTs are prepared by vacuum filtration. The electrical properties of the as-prepared, annealed and HNO3-treated SWCNT films have been investigated. It is found that the square resistance can be significantly changed upon anneal and HNO3-treatment. A room-temperature ethanol alcohol sensor based on the SWCNT film has also been demonstrated.