The DDSAM is reliable and valid for assessing and diagnosing DD in Standard Mandarin-speaking primary school children from grades 1-2. WHAT THIS PAPER ADDS?: Although a number of scales and tools have been proposed for assessing developmental dyslexia (DD) in Chinese, there is still a lack of diagnostic tools for Mandarin Chinese in Mainland China. In this study, we developed one of the most comprehensive diagnostic tools for DD in Mandarin Chinese for lower graders. We included visual-spatial attention (VA) and compounding awareness (CA), two tests that have been recently suggested as reliable measures for identifying DD in the Chinese language. This assessment tool has been verified for robust reliability and validity. This study also provided confirmation of the core deficits of DD in Chinese, which were orthographic awareness (OA). In addition, VA, rapid automatized naming (RAN) and morphological awareness (MA) were found to be the most important cognitive abilities for word reading in Chinese lower graders in this study.