The effect of al addition on the growth morphology of α-W phase in Ni-W eutectic alloy was investigated. The trajectory of the eutectic liquids trough was also estimated by thermal analysis and microstructure observation to determine the optimal quantity of al for directional solidification. The trajectory is expressed as follows: Ni-(21-X)at%W-Xat%Al, X≤5. Based upon these results, the directional solidification was carried out at the composition of Ni-16at%W-5at%Al. The composite structure was obtained under the condition of G/R/>40 (K*hr/cm2). The rods to lamellae transition shifted at a lower rate than that of the binary Ni-W eutectic. Also many growth defects were observed in the α phase. These defects may be caused by the existence of a freezing range, since the α primaries grow non-faceted, though the eutectic α phases grow faceted.