A low field magnetic resonance technique was used to analyze the water mobility character about wheat starch and its resistant starch (RS) suspensions at different water activity. RS was obtained from wheat starch by high temperature and high pressure method. Scanning electron microscopy(SEM), X-ray diffraction analysis and differential scanning calorimetry (DSC) analysis were used to evaluate the variation between the starch and RS after treatment. Compared with the original starch, it was suggested that the capacity of combining water of RS was stronger than starche from the NMR relaxation parameters, but RS's water holding capacity (WHC) was lower than that of starch. Experiments indicated that water mobility character was lower in RS. This study on the water mobility character of starch and RS was significant for the starch industry, and showed the perspective of NMR and MRI technique potential utilization in the food science field.