  We develop a phenomenological theory for the family of uranium-based heavy
fermion superconductors ($URhGe$, $UCoGe$, and $UTe_2$ ). The theory unifies
the understanding of both superconductivity(SC) with a weak magnetic field and
reentrant superconductivity(RSC) that appears at the first-order transition
line with a high magnetic field. It is shown that the magnetizations along the
easy and hard axis have opposite effects on superconductivity. The RSC is
induced by the fluctuation parallel to the direction of the magnetic field. The
theory makes specific predictions about the variation of triplet
superconductivity order parameters $\vec{d}$ with applied external magnetic
fields and the existence of a metastable state for the appearance of the RSC.
