National Assessment of Educational Achievement(NAEA) of Korea which is carried out for grade 6, 9, 12 is national-wide criteria referenced assessment and science of NAEA is carried out for grade 6, 9. In this study, analyzed ability of students which is shown in 2010, 2011, 2012 NAEA of science of grade 9 focusing in chemistry. The ability of students was divided into 4 levels which is advanced, proficient, basic and below basic. An item which is solved by most students of some achievement level was treated as representative item of that achievement level. And we analyzed representative items of each achievement level, finally drew abilities of students of each achievement level. Advanced level students of grade 9 in chemistry could understand phase change related with heat flow, could mixture separation experiment related with characteristics of matter and could control variables in experiments. Proficient level students could understand phase change related with particle, could interpret data of typical experiments, and could understand that characteristics of matter was used in mixture separation. Basic level students could understand simple principle of some concept which was shown in real life, simple hands on activities of typical experiments.