The study aimed to establish an assessment model for mathematics teachers' knowledge of students' misconceptions in the "Space and Shape" domain, develop the testing tool, investigate and analyse the overall and differences in performance, and propose suggestions for improvement. The assessment model included content knowledge and performance standards. The content knowledge standard included cognition and content dimensions. The cognition dimension was subdivided into predicting the misconceptions, interpreting the misconceptions, analysing the reasons and teaching strategies to correct misconceptions. According to the division of "Space and Shape" in official curriculum standard, the content dimension was subdivided into Recognition of graphics, Measurement, Motion, and Location. 701 Chinese mathematics teachers from 8 provinces were involved to verify the assessment model. Item response theory was used to estimate teachers' performance, and combinations of response categories was used to divide the teachers' performance into three response levels: Low, Medium and High. 81% of teachers were performing at Medium and High response levels. Teachers performed the worst in Recognition of graphics and the best in Measurement. The worst performance occurred in "analysing the reasons," the best in "interpreting the misconceptions." These results have provided evidences for adjusting teacher activities, improving teacher education courses and teachers training.