The invention discloses a measurement device and a measurement method of optical parameters of a dielectric film. The measurement device comprises a sample platform assembly for placing a sample, a refractive index and thickness measurement assembly, a transmissivity and refractive index measurement assembly and a controller, wherein the refractive index and thickness measurement assembly is formed by a laser light source assembly, a polarizer, a semi-permeability and semi-reflection mirror, a circular hole diaphragm, an automatic-collimation detector and a measurement detector; and the transmissivity and refractive index measurement assembly is formed by a white-light light source, a collimation lens set which is connected with the white-light light source and is used for a collimation light path, an integrating sphere which is used for collecting light transmitted or reflected by the sample placed on the sample platform assembly, and a spectrograph connected with the integrating sphere. The measurement device disclosed by the invention has the advantages that the refractive index and thickness measurement assembly can measure the reflective index and the thickness of the sample, and the transmissivity and refractive index measurement assembly can measure the transmissivity and the refractive index of the sample, so that the measurement of various optical parameters is realized and the measurement precision is high.