Modelling ability is one of the essential elements of the latest educational reforms, and Trends in International Mathematics and Science Study (TIMSS) is a curriculum-based assessment which allows educational systems worldwide to inspect the curricular influences. The aims of this study were to examine the role of modelling ability in the generalized Grade 8 (G8) curriculum via TIMSS 2011 and to compare the G8 students’ modelling ability among the four top-performing countries (i.e., Japan, Korea, Singapore, and Taiwan) in Asia before the latest educational reforms. This study developed Modelling Ability Analytic Index-TIMSS (MAAI-T) to analyse TIMSS 2011 G8 items. There are two dimensions of MAAI-T, stages of modelling process (i.e., selection, construction, validation, analysis and application, and deployment) and levels of model complexity (i.e., Levels 1 through 4, from single factor to extended relation). The findings showed: TIMSS 2011 G8 items centred on the stage of modelling selection, and analysis and application and mainly measured Level 3 (simple relation among factors). The highest-performing country (Singapore) demonstrated Level 3 in all stages and Level 4 of model selection and deployment; while the lowest-performing country (Korea) demonstrated Level 3 only in the stages of model selection, validation, and analysis and application.