This PhD thesis presents the physics analyses with four-lepton final state in pp collisions at √s =7 and 8 TeV using data recorded by the ATLAS detector at the LHC.Four-lepton final state provides the gold-plated experimental signature to study the Electroweak and Higgs physics at the LHC.The dedicated analyses include the studies on a rare decay process of Z→4l,which has served as a "standard candle" for Higgs discovery and measurement in the four-lepton channel and the inclusive 4l line-shape measurement covering broad mass range from 80 to 1000 GeV to test the Standard Model through interplay of QCD and Electroweak effects in different four-lepton production mechanisms.In the line-shape analysis, in mass range above 180 GeV,the signal strength of the gluon-fusion component with respect to the leading order prediction is determined first time at the LHC.Furthermore, using the four-lepton events at higher-mass range, above 220 GeV, the off-shell Higgs couplings and the Higgs nature width are constraint with much higher sensitivity compared with the direct measurement from the on-shell Higgs production.