The grouping behaviour of short fatigue cracks on surface of the weld metal for TC2 titanium alloy was investigated according to the replicating experiment, and the replicas were analyzed on the basis of fractal theory. The results showed that the feature of grouping behaviour of short fatigue crack satisfies fractal equation. The value of fractal dimension increases with the cycle frequency of increasing fatigue, and the value of fractal dimension can be regarded as a parameter to express better the fatig...