Abstract: In view of the erosion of the underground gas conduit network in the city‚an evaluation index system of the network security was established．In this system‚the index weights were determined by us ing statistical methods as well as operations research．Based on the technique of mult- i index synthetic evaluation‚a model of security evaluation for the network under the influence of various factors was established‚and the standard processing method of the data reflecting the network security was investigat-
ed in paticular．The model proposed here possesses a selfe-adaptive function．The evaluation results of 316samples through this model consistented with the experts′results by the ratio of87％‚it demonstrates that this model is applicable to the problem of synthetic evaluation for mult- i index．

Key words: gas conduit network, security evaluation, mathematical modeling