A test was carried out to evaluate. the effect of Qingong Changchun capsule on decreased fluid intelligence associated with aging. Nootropil and a placebo were used as the control drugs. Random, single-blind and self-control observation methods were applied. Ninety days were spent for clinical study. One hundred and fifty-four elderly subjects were divided into three groups (Test 63, nootropil 60, placebo 31). The method of measuring intelligence was gauged by communication between subject and computer. The measure included eight parameters. The main results were as follows: In the test group, there were significant differences (P<0.01) in speed of calculation (5.9±2.5 s, 5.1±2.1 s), speed of digits and pictures (24.2±6.2 s, 21.7±6.7 s), two-digit span (2.8±1.0, 3.2±0.8) and another two parameters before and after treatment. In the nootropil group, some parameters were also improved significantly. But in the normal control there was not any evident change. The results suggest that the treatment is an effective therapy for decreased fluid intelligence with aging.