Abstract: The objective of this study was to evaluate the effect of guar gum on the digestibility of tapioca starch using Englyst method. Pasting properties,an spin- spin relaxation time( T2) of dynamic water molecule and microstructure were examined.Additionally,the microstructure change of combinations with inactivated or activated enzymes was studied to investigate blend digestion mechanism. The results showed that guar gum made combination with a loose network structure and owned bigger T2 at lower guar gum / starch ratio,which led to a higher starch hydrolysis.Resistant starch was reduced.However,the combinations at higher ratio possessed denser network structure and smaller T2. And these combinations could significantly inhibit the enzymatic hydrolysis of starch,attributed to the strong interaction between starch and gum performed as a barrier. The value added of resistant starch content was increased.