The purpose of this study is to examine the structural relationship between student experiment and some metacognitive skills: planning, checking, and monitoring their own work. In order to measure those skills, the investigator sets each 39 grade 8 student the task to make out an aluminous crystal for him or herself. The investigator, then, scores the design of the experiment, the product (an aluminous crystal), and written report in terms of interpreting data, revising the experiment, and controlling variables. The result of the analysis, using the Structural Equation Modeling (SEM), supported the direct effect of the designing skills on data interpretation and revising, the direct effect of the scientific knowledge on data interpretation, and the direct and indirect effect of interpreting data on the product, mediated by revising the experiment and controlling variables.