  A model is suggested for the bursting x-ray pulsar, GRO J1744-28, where the
compact object of the pulsar is proposed to be a strange matter star with
crusts. It is suggested that two envelope crusts shield the two polar caps of
an accreting strange stars owing to strong polar-cap magnetic fields. GRO
J1744-28 might not have a unified crust, but two polar crusts. Bursts are the
result of phase transition of polar crusts if one accreting crust is heavier
than that the Coulomb force can support. It is shown that there should be
phase-lags when bursting crust is expanded about one hundred meters. Many
calculated properties of this model, such as the phase-lags, the bursting
luminosity and the characteristic photon energy, are in agreement with
observations.
