The present article was conducted to determine root causes of poor performance by local Mongolian learners in the writing section of TOPIK. Within the framework of the study, 89 writing compositions of the 52nd TOPIK were selected and a rubric with a mark range of 0-3 was designed by modifying a standard rubric on the basis of writing composition section criteria. The composition writing performance of the local Mongolian Korean learners was evaluated by 3 readers and a result was processed by FACETS program. The result of the study suggests that it was found out that the learners were lacking skills in having basic composition writing knowledge, creating logical flow in writing, forming relevant paragraphs of ‘introduction-body-conclusion’ and using cohesions. The authors hope that the findings of the study are possible to be used for improving the Korean language teaching methods, contents and evaluation by focusing on disadvantages of Korean writing performance of Mongolian learners. (National University of Mongolia)