Abstract: The difference between ideal infinite-order fractal in mathematical sense and real finite-order fractal in physical sense is distinguished. Using scale transformation and dimension analysis，the recurrence formula for the moment of inertia of n-order fractal triangle is obtained，which leads to the final expression for the moment of inertia When n tends to infinity，the result of this expression is in accordance with infinite-order fractal objects.

Key words: dimension analysis, fractal, moment of inertia, recurrence