The invention provides a balancing system and method for a parallel battery pack. The system comprises n single batteries BT1 which are connected in parallel and provide a load R with electricity, wherein i is smaller than or equal to n and greater than or equal to 1, n is an integer greater than 1, a resistor Ri is connected with a parallel branch of each single battery in series and parallel current balancing units PCBU are arranged on a first resistor R1 to a resistor R; each parallel current balancing unit PCBU is provided with a current differential sampling line W1, a current differential sampling line W2, a current regulating input line W3 and a current regulating output line W4; and for the parallel current balancing unit PCBU corresponding to the resistor Ri, the current differential sampling line W1 is connected to a positive electrode of the single battery BT, the current differential sampling line W2 is connected to the positive electrode of the single battery BT and the current regulating input line W3 and the current regulating output line W4 are correspondingly connected with two ends of the resistor Ri. An effective balancing method for the parallel battery pack is provided and the service life of the parallel battery pack is prolonged.