This research provides second-order approximate Noether symmetries of geodetic Lagrangian of time-conformal plane symmetric spacetime. A time-conformal factor is of the form $e^{ϵf(t)}$ which perturbs the plane symmetric static spacetime, where $ϵ$ is small a positive parameter that produces perturbation in the spacetime. By considering the perturbation up to second-order in $ϵ$ in plane symmetric spacetime, we find the second order approximate Noether symmetries for the corresponding Lagrangian. Using Noether theorem, the corresponding second order approximate conservation laws are investigated for plane symmetric gravitational waves like spacetimes. This technique tells about the energy content of the gravitational waves.