A current regulation circuit includes a number of current regulation units. Each of the current regulation units includes a sampling unit, a mean conversion unit, a current integration unit, a comparison unit, and a voltage conversion unit. The sampling unit outputs sampling current signals according to output current signals of a POE port. The mean conversion unit converts the sampling current signals into mean current signals. The current integration unit integrates and converts the mean current signals output by the number of current regulation units into output reference current signals. The comparison unit compares the mean current signals with the reference current signals, and outputs comparison signals based on the comparison. The voltage conversion unit regulates the output current signals according to the comparison signals output by the comparison unit. A POE system and method are also provided.