This paper studies explicitly the Abelian spontaneously broken gauge model for scalar and gauge bosons by using perturbation expansions . It is discovered that in various renormalizable gauges (R gauge) the gauge dependent part contributed by unphysical components of inner lines in the sum of all Feynman diagrams of the same order coexists only with the outer mass shell components of outer lines. On the mass shell only the contribution by physical components is left, just as in the unitary gauge (U gauge). Thus, the identitical nature of the R gauge and U gauge on the mass shell has been shown explicitly, hence may be seen the unitarity of the R gauge. It is also shown why residue divergences appear in the U gauge, and why these residue divergences will necessarily cancal each other out, thus revealing the crypto-renormali-zability of the U gauge.