  We study the dynamic behavior of a Bose-Einstein condensate (BEC) containing
a dark soliton separately reflected from potential drops and potential
barriers. It is shown that for a rapidly varying potential and in a certain
regime of incident velocity, the quantum reflection probability displays the
cosine of the deflection angle between the incident soliton and the reflected
soliton, i.e., $R(\theta) \sim \cos 2\theta$. For a potential drop, $R(\theta)$
is susceptible to the widths of potential drop up to the length of the dark
soliton and the difference of the reflection rates between the orientation
angle of the soliton $\theta=0$ and $\theta=\pi/2$, $\delta R_s$, displays
oscillating exponential decay with increasing potential widths. However, for a
barrier potential, $R(\theta)$ is insensitive for the potential width less than
the decay length of the matter wave and $\delta R_s$ presents an exponential
trend. This discrepancy of the reflectances in two systems is arisen from the
different behaviors of matter waves in the region of potential variation.
