The aim of this study was to investigate self-directed learning ability of English major college students. The study focused on students’ motivational orientation, use of learning strategies, and the impact of these on their academic achievement. The subjects were 133 English major freshmen enrolling English grammar course at H university. At the beginning of each class, students wrote learning logs with questionnaire surveys, reflecting on their English learning experiences and strategy use. Based on the collected data, each student’s self-directed learning ability was measured, and their motivational components (motivational orientation, self-confidence, and anxiety) and cognitive components (learning styles and strategies use) were analyzed. Subjects were then divided into three academic achievement groups according to the results of midterm and final tests. The results of the analyses showed that motivational orientation was different among the different achievement groups; the high achieving group tended to be more intrinsically oriented in their learning motivation. As for the cognitive components, the high achieving group tended to use a diverse range of learning strategies more actively than the low achieving group. These findings suggest that intrinsic motivation and learning strategies use are the most significant factors influencing learners’ academic achievement. From these findings, pedagogical implications were briefly discussed, and a SBI(Strategies-based Instruction) model applicable to this group was suggested.