Anewtransientanalysismethodforthetransmissionlinecircuitsispresentedinthispaper.Basedonthesemidiscretizationofthetelegraphequations,adiscretizedtimedomaincompanionmodelsforthetransmissionlineswhichcanbeconvenientlyimplementedinageneralcircuitsimulatorsuchasSPICEisderived.Thecomputationrequiredforthemodelislinearwithtime,equivalenttotherecursiveconvolution-basedmethod.Theformulationsforbothsingleandcoupledlossytransmissionlinesaregiven.Numericalexperimentsarecarriedouttodemonstratethevalidityofthemethod.