The invention relates to the field of banknote detection, and particularly relates to a high-precision multi-path modular thickness detection device, which comprises a thickness measurement lower roller, a floating bearing assembly, a magnetic steel frame assembly, a circuit board assembly, an elastic sheet fixing shaft assembly and an elastic sheet. The specific structure is as follows: the bearing in the floating bearing assembly and the thickness measurement lower roller are opposite vertically and are non-contact; one end of the upper part of the floating bearing assembly is provided with the elastic sheet; the floating bearing assembly is arranged on the elastic sheet fixing shaft assembly through the elastic sheet; the other end of the upper part of the floating bearing assembly is provided with the magnetic steel frame assembly; the magnetic steel frame assembly is corresponding to a linear sensor in the circuit board assembly, and a modular structure is formed. The banknote thickness feature can be accurately detected, whether a banknote has an adhesive tape and a folded corner and banknotes are stuck can be detected through the banknote thickness difference detection, the detection precision is high, the noise is little, and the service life is long.