Abstract: This paper presents a statistical evaluation of the tensile strength of the mullite shortfibrereinforced aluminium composite, which was produced by squeeze casting, by means of Weibull statistics. The result shows that the material has a high and reliable tensile strength. Volume fractions (Vf) of fibres in the material and on the fracture have been statistically analyzed. The spread of fibres shows a heterogeneity in microstructure. Two kinds of fibres, one making a small angle with the normal of the observed surface or with the tensile direction and another making a big angle with that, have hardly equal Vf. The latter has a larger Vf than the former, and the larger the Vf on the fracture, the less the tensile strength. The reason that the composite fails is the debonding of interface between the largeanglefibre and the matrix. The reason that the strength distributes in a certain range is the heterogeneity of the largeanglefibres.