This study investigates measures for second language (L2) writing development. A T-unit, which has been found the most satisfactory unit of analysis for measuring L2 development in English, is extended to measure L2 Chinese writing development through a cross-sectional design in this study. Data were collected from three L2 Chinese learner groups (n = 116) at different proficiency levels determined by institutional status, namely year of study and a native control group (n = 66). A T-unit in Chinese is firstly defined and then solutions for questions of practicality faced in extending T-unit analysis to Chinese are provided. In order to confirm the reliability of T-unit length as a measure for Chinese, T-unit analysis is applied to L1 Chinese before it is used to measure L2 Chinese development. With T-unit length being established as a reliable measure in L1 Chinese, three specific T-unit measures, namely T-unit length, error-free T-unit length, and percentage of error-free T-units, are extended to measure L2 Chinese writing development. Percentage of error-free T-units is found to be the only measure that discriminates between all levels of this learner cohort. Significance of the findings and relevance to measurements of L2 writing development in general are discussed.