Underground　pipe　networks　are　important　components　of　lifeline　engineering.　The　system　reliability　analysis　method　and　reliability-based　seismic　design　method　of　buried　pipe　networks　are　developed　on　the　basis　of　the　finite　element　model　of　underground　pipe　networks,　the　random　seismic　field　model　based　on　the　physical　mechanism　and　the　probability　density　evolution　method.　By　applying　the　methods,　the　complete　probability　density　function　and　the　system　reliability　of　the　buried　pipe　network　can　be　obtained.　Furthermore,　with　the　typical　buried　pipe　network　taken　as　an　example,　the　proposed　new　design　method　is　demonstrated.　The　innovation　of　the　method　can　be　explained　that　firstly　the　method　is　developed　aiming　at　the　entire　underground　pipe　networks　instead　of　only　simple　pipelines;　secondly,　with　the　method,　the　random　response　information　for　different　parts　of　the　pipe　networks　and　the　entire　pipe　networks　can　be　completely　obtained,　so　that　the　seismic　reliability　of　the　structures　can　be　assessed.　As　a　result,　the　seismic　design　of　the　underground　pipe　networks　based　on　the　global　reliability　can　be　realized.　©　2021,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.