The triad dimensions of complexity, accuracy, and fluency (CAF) has been widely used for assessing second language performance and development. Unlike accuracy and fluency, the construct of Chinese syntactic complexity has not been comprehensibly conceptualized or operationalized. Moreover, not tailored to the typological differences such as the topic prominence of the Chinese language, measures developed globally were found not as valid for Chinese syntactic complexity assessment as they are for Indo- European languages. Research indicated that the mean length of the T-unit of native Chinese speakers is shorter than that of L2 Chinese speakers (Jin, 2006; Yuan, 2009). For situations where research findings developed globally are not as applicable when indiscriminately applied to typologically different languages, this dissertation employed the notion of "GlobaLocality" to define and assess Chinese syntactic complexity. First, globally, clause combining was revisited to subsume the topic chain in addition to coordination and subordination. An organic approach was then adopted to investigate complexity via global, clausal, and subclausal levels (Norris & Ortega, 2009). Second, locally, a taxonomy of Topic-Comment units (TC-units) was proposed to examine Chinese syntactic complexity: the number and the nature of a terminable TC-unit's components; and the number and the nature of their constituent relationship. Third, by performing discriminant function analyses on L1 and L2 Chinese speakers' spoken (N = 115) and written (N = 116) output elicited from a designed online test, a series of proposed TC-unit based measures were confirmed with high efficiency (61.2%~76.5%) at proficiency group membership classification. Lower-proficiency speakers produced shorter terminable TC-units consisting of fewer single TC-units, whereas higher-proficiency speakers produced longer terminable TC-units in the form of varied topic chains consisting of more single TC-units. Chinese syntactic complexity development along proficiency increase also displayed a transition from more lengthening to more combining of single TC-units. Fourth, utilizing TC-unit based measures, repeated measures analyses observed more complex language produced in more complex tasks along the resource-directing dimension. Immediate task repetition was observed to lower learners' communication anxiety and improve learners' self-perceived performance. Last, this dissertation provided suggestions on complexity descriptions for proficiency guidelines and on how to develop Chinese syntactic complexity in classroom instruction. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]