Approximately 6% of the population are estimated to have difficulties with learning about numbers and arithmetic, generally regarded as dyscalculia (or mathematics learning disability). As no standardized procedure for identification of dyscalculia for primary students is currently available in Hong Kong, this study aimed to develop a math achievement test in identifying at-risk Primary students for dyscalculia, as a first step to serve this purpose. A sample of over 1000 Grade 1 to 6 students were invited to complete a comprehensively designed math achievement test, and items were selected based on their functioning. The finalized scales had good reliability and validity. The test provides psychologists and teachers a tool to assess students’ math achievement and may potentially serve as a diagnostic tool of at-risk Primary students for dyscalculia in Hong Kong. All rights reserved.