This study developed a Checking Assessment for Single-Step Word Problem-Solving for Addition and Subtraction (CA-SSWPS-AS) using componential and content analyses. The checking ability component was divided into two dimensions: reflection and error detection. The reflection dimension consisted of checking actions and checking skills, whereas error detection comprised errors in answer calculation, operational procedure, problem semantic context, and quantitative information catching, as well as a correct (no error) facet. The single-step word problems for addition and subtraction were derived from various mathematics textbooks for first and second graders in Taiwanese elementary schools. Componential and content analyses were used to examine the checking operations and semantic schema involved in single-step word problem-solving for addition and subtraction. The results were then used in development of the CA-SSWPS-AS. Considering the homogeneity of learning contents and experiences in different schools, 864 second graders from Chiayi City and Chiayi County in Taiwan were selected as participants through convenience and cluster sampling. All participants were tested using the CA-SSWPS-AS combined with experience preactivated tasks in single-step word problem-solving for addition and subtraction. The data were divided into two clusters for use in random cross-validation statistical analyses. Validity analysis using exploratory and confirmatory factor analysis produced a number of factor structures that matched the aforementioned two dimensions and their facets. The variance proportions of factor extraction and model fitness were positive, as was criteria-related validity (using students’ scores assessed by teachers in classroom performance-checking as criteria). Reliability analysis demonstrated a positive α coefficient and composite reliability. Regarding item analysis, the critical ratio was strong, regardless of whether a single item, a subassessment, or the whole was analyzed. Finally, reflection and error detection performance varied significantly when checking individuals with different word problem-solving performances.