We first review fundamental ideas of Kaluza-Klein theory and discuss various problems in constructing a realistic unfied theory of elementary particles and gravitation based on the Kaluza-Klein theory. In the main part of this thesis we show i) The four dimensional BRS symmetry can be obtained correctly through the Kaluza-Klein dimentional reduction from the higher dimensional BRS symmenty, and the physical S-matrix can be established in the whole quantum Kaluza-Klein theory including both massless and massive modes. ii) The gyromagnetic g-factor of massive fields in the Kaluza-Klein theory is unity, which is one of the special features of massive fields in the Kaluza-Klein theoty.