  A recent observation has shown that PSR B1257+12 could have quite small X-ray
emitting area, only about 2000 m$^2$, which is more than three orders smaller
than the canonical polar cap size. We suggest here that PSR B1257+12 could be a
low-mass quark star with radius of $R \simeq 0.6$ km and mass of $M \simeq
3\times10^{-4}\msun$. Such a low-mass quark star system may form in an
accretion induced collapse process or a collision process of two quark stars.
