Moral weakness is one of the important issues of the psychology of ethics, which deals with why and how the gap between knowledge and moral action appears. In a comprehensive definition, this phenomenon can be considered as a conscious action against the belief, judgment and principles that a person has accepted morally. Moral weakness or the problem of the gap between moral belief and action and the solution to fill this gap is one of the fundamental concerns of all people who have a heart for a virtuous life. In the meantime, one of the sciences that has a suitable capacity to explain this phenomenon and to express a solution for the treatment or prevention of this phenomenon, and which has received less attention, is the science of psychology. For this reason, the upcoming research with analytical method and using library resources aims to explain the factors affecting the occurrence of this problem and also the solution to prevent this phenomenon by paying attention to the great capacity of this knowledge and focusing on its cognitive approach. The results of the research indicate that imitation, lack of strengthening the power and rational reasoning, as well as irrational justification can be considered as the phenomena of moral weakness, and this weakness can be avoided by avoiding the acceptance of imitation words and mainly through argumentative discussions between educators and also Ethical riddles were designed to strengthen this issue by the trainers, as well as taking role models from moral people.