The self-determination theory (SDT) offers a parsimonious, internally consistent framework for systematically describing many different orientations in a comprehensive manner. Within the SDT framework, the four main types of motivation, i.e. intrinsic motivation, self-determined extrinsic motivation, non-self-determined extrinsic motivation, and amotivation exist along a dynamic continuum. SDT sheds light on L2 motivational study and learner autonomy. The present study aims to examine the grneralizability of the SDT’s theoretical framework in the Chinese context by looking into the motivational differences between the proficient and the less proficient students in English learning. The research questions are:1) Are the Chinese students also characterized by the seven orientations in terms of self-determined motivation (namely, amotivation, external, introjected, identified, intrinsic motivation-knowledge, intrinsic motivation-accomplishment and intrinsic motivation-stimulation) and the continuum patterns?2) Are the proficient students more self-determined in English learning than the less proficient students? If it is true, in what ways do the two groups differ from each other in their sub-motivations comprising motivational complexes?Students from both proficient group (N=350) and less proficient group (N=312) were measured on their motivation for English learning by using the questionnaire adapted from LLOS-IEA (Language Learning Orientations Scale—Intrinsic Motivation, Extrinsic Motivation, and Amotivation Subscales) by Noels, et al (2000). Statistical analysis of the questionnaire scores indicated a pattern of correlations reflecting a continuum of increasing self-determination, from amotivation to less self-determined forms of motivation (i.e. External and Introjected Regulation) to more self-determined forms of motivation (i.e. Identified Regulation and Intrinsic Motivation). Meanwhile, by comparing the orientations of the proficient group and the less proficient group, it was found that the proficient students tended to be more autonomously and self-determinedly motivated than the less proficient group, though the external orientation was evident in both groups. Basing on the interview with eightstudents from the two groups, the various factors facilitating or undermining the intrinsic motivation as well as the internalization process are discussed. Finally, suggestions for English language teaching are put forward.