In　this　paper,　the　perturbation　based　on　displacement　method　was　extended　to　the　field　of　circuit,　which　is　used　to　solve　the　nonlinear　LC　circuit　equation,　and　an　analytical　method　for　the　research　of　nonlinear　LC　circuits　was　provided.　Deducing　from　the　Lagrange　function　of　the　system,　the　variational　equation　was　discretized　by　the　finite　element　to　obtain　the　time　stiffness　matrix.　The　characteristic　equation　of　the　circuit　was　perturbed　for　the　first　time,　and　the　original　time　stiffness　matrix　was　replaced　by　a　perturbed　approximate　stiffness　matrix.　On　the　basis　of　the　relationship　between　the　stiffness　matrix　and　the　transfer　matrix,　the　problem　was　transformed　into　the　problem　of　symplectic　transfer　matrix,　and　the　oscillation　characteristics　of　the　LC　circuit　can　be　solved.　The　comparison　between　the　perturbation　based　on　displacement　method　and　the　fourth　order　Runge　Kutta　method　demonstrated　the　correctness　of　the　proposed　method.　Compared　with　the　transfer　symplectic　matrix　method,　it　is　proved　that　the　proposed　method　has　definite　precision,　efficiency　and　stability.　©　2019,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.