1 Language Learning Strategy used by Senior High School Students and its Influence on their Achievement Semi Sukarni English Education Program, Purworejo Muhammadiyah University, Central Java Indonesia semi.sukarni24@gmail.com. Abstract The aims of the study are to investigate the Language Learning Strategy (LLS) used by Senior High School students and analyze the influence of the LLS on their English achievement. The research had been done in two Senior High School in Purworejo. There were 117 participants in the study. Strategy Inventory and Language Learning (SILL) questionnaire and documentation were used to collect the data. The data were analyzed using descriptive and inferential analysis. To test the hypothesis, correlation product moment and linear regression were applied. The result of the study shows that metacognitive strategy is the most frequently used by the students. It is followed by compensation, cognitive, memory, social and effective strategy. The second finding shows that there is a positive and significant correlation between the use of LLS and English achievement as the r-value is 0.562 with the sig. 0.000. The regression test shows that LLS contributes 31.5% to the achievement while 68.5% was contributed by other factors. The implication of the study is it is important to develop teaching models which provide students the opportunity to practice the LLS during the learning process. The English teachers can also use Strategy-based Instruction for teaching LLS which is integrated into the learning tasks. Keywords: Achievement, influence, LLS, metacognitive, Senior High School Introduction There are many factors influence language achievement. It includes internal and external factors. The internal factor related to individual factors as age and sex. Related to age Krashen as cited by “the younger the better”. This is fact often contradictory with the practice of language learning in Indonesia as the language learning officially taught at secondary school at the age about thirteen. Other factors like attitude, motivation, anxiety, learning style, learner belief often called by individual differences (Davies & Elder, 2004, Dornyei, 2005, Freeman & Long, 2014) can also influence the language learning. English teachers must also pay attention to these factors and cannot neglect them. Besides the above factors there is still other individual factor called learner actions (Freeman & Long, 2014) namely learning strategies and communication strategies. In other words, it is called tactical (Kumaravadivellu, 2008). Learning strategies are tactics or techniques or ways how learners empower themselves in the language learning process in broad language aspects and skills. While communication strategies are also considered as tactics which are used to avoid the communication breakdown. Learning strategies and communication strategies are important factors which can influence learning achievement. Finally, external factors which related to environmental includes social contexts and educational contexts (Kumaravadivellu B, 2008). Social context refers to the home, the neighborhood, classroom, and society. Whereas, educational contexts that shape language policy, language planning and the language opportunities available for the language learners (Kumaravadivellu.B, 2008). However, in this paper the writer will not discuss broadly the language factors, the writer will only focus on learner action or language learning strategies (LLS) as it is quite an influential factor to the language achievement. There are some studies related to language learning strategies