To put the quantum tunneling problem of a singular potential on a physical basis, two methods are usually used: the limiting cutoff procedure of the region of singularity and the matching of the wave function and its first derivative at two sides of the singular point. These approaches, nevertheless, effectively suppress the mathematical essence of the singularity. Hence the natural question of how quantum tunneling will behave when the singularity is preserved as much as possible is the main question of this paper. We get that the Coulomb singularity is reflected as infinitely accelerating oscillations in the transmission coefficient between zero and one when the incident particle's energy approaches the zero boundary. At relatively high energies, the tunneling acquires the character inherent in regular potentials, and becomes completely transparent in the asymptote.