<p>Abstract<br />The purpose of this research was to improve the writing ability of argumentation of STKIP Melawi students.<br />The method used in this research was quasi experimental method with nonequivalent control group design.<br />The results of this study were 1) the average pretest of students' argumentation ability of control class was<br />54,94, while posttes 57,20, while experimental class got pretest average value 51,44, and posttes 80,04; 2)<br />There was no significant difference in the ability to write argumentation on pretest tests between the control<br />group and experimental group, whereas in the posttest there was a significant difference in the ability to write<br />argumentation between the control group and the experimental group.<br />Keywords: the writing ability of argumentation, quasi experimental method, nonequivalent control<br />group design, pretes, posttes.</p>