This thesis concerned with a direct approach for solving three-phase distribution power flow problems. Radial distribution feeder network has been fully exploited to make the direct solution possible. Three sparse matrices are used for solving distribution feeder power flow problems. By using the sparse matrix technique, the time and storage in constructing matrix can be reduced. The multiple line spacing model is used for calculating line transmission matrix. Distances between phase conductors and neutral wires are used for the overhead and underground lines. Multiple transformer connection model is used for calculating transformer transmission matrix. By using the improved matrices, the transmission matrix model of more equipment can be included in the proposed power flow calculation.