The Alpha Magnetic Spectrometer, AMS-02, is operating on board the International Space Station since the 19th of May 2011 and has collected more than 15 billion events. The main scientific goals of the experiment are the search for antimatter and dark matter, the high precision measurement of charged cosmic ray spectra and fluxes, and the study of gamma rays in the GeV to TeV energy range. The Electromagnetic Calorimeter (ECAL) of AMS02 is required to measure e+, e- and gamma spectra and to discriminate electromagnetic showers from hadronic cascades. To fulfill these requirements ECAL is based on a lead/scintillating fiber sandwich, providing a 3D imaging reconstruction of the showers. The electronics, with low noise and challenging dynamic range readout, were designed following stringent requirements on mechanical and thermal stability, power consumption, radiation hardness and double redundancy. The full system had successfully gone through the space qualification tests. AMS-02 was tested during Summer 2010 in a test beam at CERN, using 10 to 250 GeV electron and positron beams and proton beam at 400 GeV. After presenting a summary of the AMS02 performance in space, results on the measurements of ECAL parameters and its performance will be reported.