The cognition processes of students with autism spectrum disorder (ASD) in solving mathematical problems is still rarely studied in depth, although the prevalence of the students is increasing. The purpose of this research was to describe the cognition processes of students with ASD in solving mathematical problems. The subjects in this research are two high school students with high functioning ASD. Data was gathered from task-based interviews. The cognition processes in solving mathematical problems involved reading and paraphrasing the problems, visualizing the problems and representing them in the form of drawings or diagrams, determining the hypothesis to create a plan to solve the problems, estimating or predicting an answer to the problem, completing computations, and finally, checking to ensure the process of problem solving resulted in a correct answer. Some characteristics of students with ASD were very perceptible during mathematical problems solving process. Differences in intelligence of the both subjects had a role in every process of cognition.