[en] Description of the injection system of the PETRA storage ring with circulating current of 2x30 mA contained in 2x4 bunches is presented. Principle of operation is described. In the injection system every 20 ms a train of positron bunches separated 32 ns from each other is accelerated in Linac 2 up to 300 MeV and then injected into DESY for acceleration up to 2.2 GeV. At 2.2 GeV these bunches are transferred to DORIS for accumulation. It will be reinjected into DESY, accelerated up to 7 GeV, transferred to PETRA and accumulated there. For the present all elements of the 7 GeV - ejection were installed and the e^- ejection was tested. The positron transfer channel between DESY and PETRA is completed. In the single ring mode operation of DORIS acceptances of Asub(x) >= 40 mm mrad and Asub(z) <= 10 mm mrad have been achieved. The injection repetition rate is 50 Hz, the ejection rate - 10 Hz, and single bunches were transferred via DESY through the first octant of PETRA