An exponential inequality for associated random variables is established. By this exponential inequality, we obtain the rate of convergence n(superscript -1/2) (log n)(superscript 1/2) for the strong law of large numbers ∑(superscript n subscript i=1)) (X(subscript i)-EX(subscript i))/n→0 as., which reaches the available one for independent random variables in terms of Berstein type inequality.