The purposes of the research were to conduct an error analysis in paragraph writing of the students of the faculty of Liberal Arts Rajanangala University of Technology Phra Nakhon to collect information to be used as a guideline for English teaching and learning and for English curriculum development for undergraduate students of the faculty. The simple-random sample group of 36 students was 40% of the total population 88 fourth-year students in the academic year 2010. The tools were a paragraph -writing worksheet and a form prepared to record the frequency of each type of errors ofeach sample The results of the study indicated that among four main types of errors : 1) paragraph format 2) paragraph structure 3) Grammar and sentence structure and 4) punctuation and mechanics it was found that errors in grammar and sentence structure were most frequently found (58.72%). This included 11 types of errors in the order of frequency found as follows: word choice verb forms detelminers sentence fragments prepositions singular/plural nouns verb-tenses run-on sentences subject-verb agreement wrong word order and use of reference terms accordingly.