In order to evaluate the characteristic of performance ability which has to do with stability of performance in track and field, one-parameter logistic function was utilized to describe the achievement probability curve based upon the assumption that athletic performance distributes as normal during such a short period that the ability could not be assumed to change. A parameter of logistic function was used as random variable denoting characteristic of performance ability, because it determines the maximal slope of logistic function and the distribution range of records. About 95% of samples showed successful application of the function. Logistic function parameter; athletic performance characteristic, was different among the athletes and did not show any relationship with records. This is why this parameter is effective for evaluation of one aspect of performance ability.