Neuropsychological test can objectively evaluate the severity of cognitive impairment. It is an effective means to detect disease progression and evaluate drug efficacy. Comprehension test is an important part of cognitive impairment assessment for the elderly. The assessment is performed by judging whether the subjects make accurate actions according to the instructions, which is conducive to the early prevention and early intervention of dementia. This study proposed a video analysis method of human posture estimation for comprehension detection in neuropsychological testing. The coordinates of key points of human body were first extracted based on OpenPose. Then, based on the image morphology processing technology and Fast R-CNN, a two-dimensional coordinate extraction method was proposed for the key points of the specified target objects, such as paper and toothbrush. Also, the mathematical model of human posture estimation was established. Six actions of neuropsychological test were tested to verify the effectiveness of the proposed method. The results show that the proposed mathematical model of posture estimation and interactive action recognition method can effectively detect human posture action commands and interactive instructions.