A novel tri-layer Si-based micro-cantilever thermal infrared (IR) detector with carbon nanotube (CNT) film is fabricated. It is based on the characteristic that the composite micro-cantilever bends in response to incident IR thermal radiation due to the bi-material effect. The bending of micro-cantilever is piezoresistively detected. Furthermore, a new IR absorbing layer material --- CNTs --- is coated in order to enhance IR radiation absorbing characteristic. the micro-electro-mechanical system (MEMS) sensor could be compatible with integrated circuit technology.