Power grid suffers tremendous economic loss in extreme ice disaster weather, suggesting that it lacks immediate precautionary system. On the basis of the standards of Q/GDW179-2008 and IEC60826-2003, the curve of transmission line design loads is built up. In view of ransom character for load-strength of transmission line, according to load-strength interference theory, a short-term wind and ice loading risk model is established, which is a time-dependent wind and ice loading model, and can be calculated unreliability probability and fault rate, showing risks about cluster fault and common fault. Furthermore, wind and ice loads are divided into five states, which show risk margin of loads. It also can provide precautionary information for operator, and can present risk measurement on time scale.