The deep centers in Si-implanted LEC semi-insulator gallium arsenide have been carefully studied using the deep level transient spectroscopy (DLTS) technique. The results are as follows. The four majority carrier traps,E01 ,E02,E03 and E04 have been observed in the active regions of the Si-implanted LEC semi-insulator gallium arsenide after high temperature an-nealling, and their electron apparent activation energies are 0.298, 0.341, 0. 555 and 0. 821 eV respectively. The E04 trap is related to the EL2. The activation energy of the electron capture cross section of E04 is 0. 119 eV Three minority carrier (hole) traps have been newly found in the same active regions. The hole apparent activation energy of the H03 trap is 0. 713 eV and its concentration is about 2. 8×1016cm-3.