Superitem test based on the SOLO model (Structure of the Observing Learning Outcome) has become a powerful alternative assessment tool for monitoring the growth of students' cognitive ability in solving mathematics problems. This article focused on developing a superitem test to assess students' algebraic solving ability through interview method. The interview data analysis found that the high ability students seemed to be more able to seek the recurring linear pattern and identify the linear relationship between variables. They were able to coordinate all the information given in the question to form the algebraic expression and linear equation. Whereas the low ability students showed their abilities more on counting and drawing method. They lacked understanding of algebraic concepts to express the relationship between the variables. The findings provided evidence on the significance of superitem test in assessing algebraic solving ability. (Contains 2 figures.)