A composition, a method fabricating the infrared ray transmitting filter, and an infrared ray sensor are provided. When the composition forms a film with a thickness of 1 μm, transmittance of the film in a wavelength in a range from 400 nm to 700 nm is less than 4%, and transmittance of the film in a wavelength in a range from 900 nm to 1300 nm is more than 90%. The composition comprises an alkali-soluble resin at least containing an acrylic group, a carboxyl group, and a fluorene ring, a photoinitiator, an unsaturated monomer, a pigment mixture, and a solvent. The pigment mixture is formed by mixing a colorant dispersion and a pigment in a weight ratio from 60:40 to 70:30.