  The Three-Body Parameter(3BP)
$a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-}$ is crucial to understanding
Efimov physics, and a universal 3BP has been shown in experiments and theory in
ultracold homonuclear gases. The 3BP of heteronuclear systems was predicted to
possess much richer properties than the homonuclear counterparts for the large
parameter space. In this work, we investigate the universal properties of
$a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-}$ for the
Heavy-Heavy-Light(HHL) system with negative intraspecies scattering length
$a_{\scriptscriptstyle HH}$. We find that
$a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-}$ follows a universal behavior
determined by the van der Waals(vdW) interaction and the mass ratio. An
analytic formula of $a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-}$ is given
as a function of $a_{\scriptscriptstyle HH}$, which allows an intuitive
understanding of how does $a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-}$
depend on the mass ratio and the vdW length $r_{\scriptscriptstyle vdW}$. In a
special case, when the two heavy atoms are in resonance,
$a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-}$ is approximately a constant:
$a^{\scriptscriptstyle(1)}_{\scriptscriptstyle-} = -(6.3\pm0.6)\,
r_{\scriptscriptstyle vdW,HL}$.
