Heavy neutrinos can be discovered at LHC. Many extensions for Standard Model predict the existence of a new neutrino which has a mass at high energies. B-L model is one of them which predict the existence of three heavy (right-handed) neutrinos one per generation, new gauge massive boson and a new scalar Higgs boson which is different from the SM Higgs. In the present work we search for heavy neutrino in 4 leptons + missing energy final state events which are produced in proton-proton collisions at LHC using data produced from Monte Carlo simulation using B-L model at different center of mass energies. We predict that the heavy neutrinos pairs can be produced from new gauge neutral massive boson decay and then the heavy neutrino pairs can decay to 4 leptons + missing energy final state which give us an indication for new signature of new physics beyond Standard Model at higher energies at LHC.