1. A control system of a brain computer interface (BCI) with a stepping delay flickering sequence, the control system comprising: a flickering sequence generating unit for generating a plurality of different flickering sequence signals by encoding a static flashing segment and a plurality of stepping delay flashing segments divided in different time sequences, wherein the static flashing segment of each of the flickering sequence signals has a plurality of flashing cycles, and the flashing cycles are corresponding to a static flashing frequency, wherein a proportion between bright and dark sections in the flashing cycles is adjustable; a display unit which is electrically coupled to the flickering sequence generating unit, and comprises a plurality of display areas for displaying a plurality of target images corresponding to the flickering sequence signals; a measuring unit which is connected to an organism through an electrode, and is used for acquiring a response signal generated by the organism evoked by the target images; and a signal processing unit which is electrically coupled to the measuring unit and the flickering sequence generating unit, and performs signal processing on the response signal by using a mathematic method to distinguish which one of the target images is gazed by the organism, so as to generate a corresponding controlling command.