The invention relates to a sarsasapogenin structure modified derivative and is characterized in that the structural formula of the sarsasapogenin structure modified derivative is shown as formulas (I) and (II) which are shown in the description. The invention further provides a pharmaceutical composition application of the sarsasapogenin structure modified derivative. Activity tests aiming at AD related target spots show that a number of newly synthesized compounds have activity superior to that of a lead compound. The sarsasapogenin structure modified derivative has a high practical value in curing senile dementia, makes up for the shortage of a sarsasapogenin structure modified derivative in the prior art and is of great significance.