The flow distribution characteristics in piping arrangements of sprinkler system have been investigated in this paper by the numerical simulation. While the exit flow rates of loop type piping arrangements predicted by the three-dimensional CFD calculation and those given by the design flow rate show a close agreement, the results of the general type piping arrangement are found to differ from the design flow rate by -19.1% to 27.3% for the various exits. These discrepancies may be attributed to the underlying limitation concerning the fitting loss coefficients, which assume that the flow in front of the fittings is fully developed. Consequently, loop type piping arrangement of sprinkler system must be selected in order that the flow rate may be balanced.