Dementia is a very common disease among the elderly, and its main symptom is cognitive dysfunction. Relevant research suggests that the course of dementia can be delayed through non-pharmacological intervention. Therefore, the purpose of this research is to develop a cognitive training system with the aid of digital technology to help people with dementia strengthen their brain and slow their cognitive function degradation. This research cooperates with the Changhua Christian Hospital in Taiwan, and the research subjects are a total of 16 mild dementia patients with an average age of 79.6 years old, who are divided into a traditional group and a digital group. The experimental tool is the “Recall” digital cognitive application system, as developed by this research, which includes sharing nostalgic storytelling and the introduction of technology for cognitive training. There are five types of systematic cognitive training questions: quiz questions, calculation questions, puzzle questions, weight questions, and silhouette questions, which mainly train memory, logic, and concentration. After treatment, the subjects are investigated via behavior observation, questionnaires, and interviews to learn their perceptions of the usability and experience of digital cognitive application systems for patients with dementia, and the Pearson correlation coefficient is used to analyze the relevance of the four factors of the experience, namely, feel, sense, relate, and think. The results show that the experience of using this system is significantly related in the factors of sense, relate, and think. On the whole, the application system developed in this research should have benefit in the introduction of technology into reminiscence therapy for patients with mild dementia via cognitive training through games.