A theoretical analysis was carried out on the torsional characteristics of directionally solidified Al-Al₃Ni eutectic composites. The torsional properties of the eutectic composites and the matrix were tested in order to estimate the torsional behavior of pure Al₃Ni fiber by means of the rule of mixtures. The Ludwik`s equation T=Hγ^n was used to represent the shear stress and strain relation. The stress coefficient, H and strain hardening coefficient, n were obtained by minimizing the errors between the Torque-twist angle curve and the experimental data. The calculated Torque-twist angle curves using Ludwik`s equation were shown to closely fit the experimental results, and the calculated stress and strain hardening coefficients of pure Al₃Ni fiber were 836,000∼881,600 KN/㎡ and 1, respectively. The rule of mixtures was more applicable for the torsional behavior than for the tensile behavior.