Under the condition that load and its increasing pattern is uncertain， a novel voltage stability evaluation model withinterval expression is given. This model can tackle the interval characteristics of the variables and can consider the probabilitydistribution of these variables. The proposed approach provides a new light for static voltage stability evaluation underuncertain conditions. Linear programming is employed to solve this shortest path problem with two terminals being not fixed.At last， the speed and efficiency of the proposed method are tested on IEEE 30-bus power system.