Among many characterization methods for the compatibility of blends, the rheological ones have attracted more and more attention due to its sensitive response to the changes of structure of blends. In this work, PVC and PLA blends were prepared by melt mixing in torque rheometer. Static and dynamic rheological responses were used to analyze the compatibility of PLA/PVC blends, and a variety of analytical methods were also used, such as SEM and DSC, to assist revealing the phase morphology of the blends. The results showed that PVC/PLA = 50/50 formed a co-continuous phase structure, the other ratio blends formed a "sea-island" structure. The blend with co-continuous structure exhibited the lowest viscosity, the highest non-Newtonian index and the lowest entrance pressure drop, and the phase separation was more difficult than those with "sea-island" structures. It was concluded that the blend with co-continuous phase structure showed the strongest rheological responses. PVC/PLA = 50/50 also showed the highest impact strength among the blends.