A pixel driving circuit includes a current controlling module, an outputting module and a time length controlling module including a comparator, a first energy storage element, an offset voltage writing sub-circuit, and first and second output sub-circuits. First terminal of first energy storage element is connected with first input terminal of comparator and second terminal with the first output sub-circuit. The second output sub-circuit is connected with second input terminal of comparator. The offset voltage writing sub-circuit writes an offset voltage of comparator to the first energy storage element. One of the first and second output sub-circuits outputs time signal and the other outputs reference voltage signal. The comparator outputs comparison signal according to the time signal and the reference voltage signal. The current controlling module outputs current signal. The outputting module turns on responsive to the comparison signal and controls current of light-emitting unit according to the current signal.