Short circuit capacity is a measure of the robustness of power system voltage. A new method is proposed to use short circuit capacity analyzing voltage stability. The analytical relationship between the short circuit capacity and the voltage stability of the low-voltage load bus is derived. Based on the Thevenin's equivalent for the power source side， the voltage stability analysis with the equivalent load model for the distribution network well matches the actual situation without adding the scale of simulation system. The derived critical minimal short circuit capacity for maintaining voltage stability can directly quantify all the effects on voltage stability due to the changes of the distribution load side， which is a comprehensive voltage stability parameter. By comparing the actual short circuit capacity and the critical minimal short circuit capacity， the voltage stability of the bus could be fast assessed. By tracking the changes of the two capacities， the main reason causing the voltage instability can be determined. Therefore it will provide a clear guide for the voltage stability control. The work is theoretical support for applying short circuit capacity on the on-line assessment and control of wide-area voltage stability.