Assessment at preschool age plays a crucial role in the process of learning especially for children with autism spectrum disorder (ASD), whom encounter communication difficulties as exchanging thoughts or information by speech, writing or nonverbal expression. Therefore, a welldesigned assessment method is necessary in order to guide learning and serve as a powerful tool to reinforce children's motivation to learn. Information about what a child with ASD knows, understands and is able to do is used by tutors to adjust their teaching strategies. All assessment methods have different purposes before, during or after instruction. Besides, formative assessment is the most recommended type that helps improving children's learning and it takes place during the learning process. Also, serious games provide a context for assessing a broader range of skills and constructs compared to traditional assessment approaches. In this article, we propose a new technique for evaluating the degree of concept's assimilation of children with ASD through serious games. It allows identifying concepts that children are struggling to understand and skills they are having difficulty acquiring.