诊断性语言测评包含诊断、反馈和补救学习三个核心要素，但相关研究很少关注补救学习的效果。本研究基于优诊学诊断测评工具，对比了诊断测评补救学习对高、低水平学习者英语语法学习的促学效果。结果表明：相较传统学习模式，语法诊断测评显著提升了学生的语法学习。实验组比控制组在复合句、倒装和情态动词三个微技能上有显著提高，但高、低水平组提高的微技能存在差异，高水平组虚拟语气和倒装两项技能进步明显，低水平组复合句技能进步明显。上述维度正好对应了各自水平组的相对弱项微技能，表明诊断测评对提升弱项微技能的效果更加显著。与此同时，高水平学生比低水平学生在介词微技能的提升更高，表明语言水平可能会影响诊断测评的促学效果。

Diagnostic language assessment (DLA) consists of three core components: diagnosis, feedback, and remedial learning, yet the effectiveness of remediation is largely ignored. Utilizing the online platform of Udig, this study examined the effects of the computer-mediated DLA on the grammar learning of Chinese EFL learners with high and low proficiency level. Results showed that the computer-mediated DLA system was more effective in improving learners’ grammar learning than traditional approaches. Compared with the control groups, the experimental groups made greater improvement in three sub-skills, namely, compound sentence, inversion, and modal verb. The specific improved sub-skills varied between high and low level EFL learners, with greater improvement in subjunctive mood and inversion for high-level students, but more improvement in complex sentences for low level students. These respective sub skills correspond closely to the relative weaknesses for both levels of students, indicating that DLA might work more effectively on learners’ weak skills. Results also showed that, compared with low-level students, high-level students improved significantly in the preposition sub-skill, suggesting that EFL proficiency might be a factor impacting DLA effects on grammar learning.