Calibration of jets are important in the studies of new physics, since when jets are better calibrated, the new physics events can be better reconstructed and differentiated from the background. In semi electronic ttbar events, the reconstructed jets originate from the decay of the W boson and the top quark. Since the hadronic part of signal events, can be fully reconstructed, however, the leptonic part, where the W boson decays leptonically; can not be fully reconstructed due to the presence of a neutrino in the final state. As the masses of both the W boson and the top quark have been already measured at LEP and Tevatron with great precision, therefore, the mass values can be used to constrain the system. Mass constraints are imposed in an event-by-event least square technique by means of Lagrange Multipliers which is referred to as a kinematic fit. The kinematic fit return a probability which reflects how likely the hypothesis of originating three reconstructed jets from the decay of the top quark is correct. The jet energy scale calibration factors are then adopted so that the probability returned by the kinematic fit is maximized. The results are obtained based on a simulated data sample corresponding to an integrated luminosity of about 100 pb-1 . It is shown that the estimated results are comparable with the expected values among the statistical as well as systematical uncertainties. Since March 2010, the LHC machine has been running at a center of mass energy of 7 TeV and the CMS experiment has been collecting the proton collision data. The amount of data collected in 2010 has reached to about 36.1 pb-1. The method is also applied on the 2010 collision data recorded by the CMS experiment and the results have been reported. Good agreement between simulation and collision data is found. The results are statistically limited which can be fixed when running the method on larger amount of statistics collected in the 2011 runs. Keywords : Standard Model, top quark, Jets, Electron, MVA, Kinematic Fit, CMS, LHC, CERN