  Let $X$ be a Gorenstein minimal projective $3$-fold with at worst locally
factorial terminal singularities. Suppose that the canonical map is generically
finite onto its image. C. Hacon showed that the canonical degree is universally
bounded by $576$. We improved Hacon's universal bound to $360$. Moreover, we
gave all the possible canonical degrees of $X$ if $X$ is an abelian cover over
$\mathbb{P}^3$ and constructed all the examples with these canonical degrees.
