In this paper， the microstructure， crystal properties and particle size distribution of purple sweet potato starch and its dough were studied， Farinograph， RVA and rheological properties of purple sweet potato starch-wheat flour dough were analyzed， and the correlation between starch and dough was analyzed. Starch granules of purple sweet potatoes all exhibited round and hemispherical shapes. The average particle range was 43.903 to 55.842 μm， and the volume distribution was three-peak distribution. X-ray powder diffraction patterns revealed purple sweet potato starches were CA-type with relative crystallinity varying from 36.760% to 54.280%. The formation time and stabilization time of purple sweet potato starch dough were in the range of 2.20~3.90 min and 3.20~4.10 min， respectively， and other gelatinization properties decreased with the increase of gelatinization temperature between 70.10 ℃ to 85.65 ℃， which was beneficial to the stability of dough， the storage modulus （G'） and loss modulus （G''） increased significantly， while the loss angle tangent （tan δ） decreased first and then increased， indicating that the degree of molecular cross-linking in the mixed system increased， which made the dough elastic and beneficial to the stability of dough. There were differences in water distribution. The correlation results showed that the crystallinity was negatively correlated with water absorption, stabilization time, weakening degree and tolerance and pasting temperature, and positively correlated with peak viscosity, peak time, minimum viscosity, final viscosity and retrogradation value. The average particle size was negatively correlated with softening and BV， positively correlated with peak time and crystallinity. This study provides a theoretical basis for the selection of starch and the cultivation of purple potato varieties special for starch dough production.