Curriculum of 2013 emphasizes the application of Scientific approach which includes observing, questioning, experimenting, associating and communicating. In fact, not all teachers are master that and teach it to their students. Purpose of this research is to assist teachers making lesson plan in designing experiment and help students to lern in designing experiment. The respondent were 27 students grade 8. Metode of this research is research action class. Instruments used were lesson plans in designing experiment, observation sheets, cognitive test sheets, and questionnaire sheets. Data analyzed in qualitative descriptive. The results showed an average 84.82% of students were able to design the experiment with help of stimulant questions. This is supported by questionnaires filled out by students, the results show that on average 85.93% of students stated it was helped by stimulant question when designing experiments. The test results showed an average 82.96% of students were able to design experiment with  help of stimulant questions. From the results of the study can be concluded that through stimulant questions, students can skillfully design the experiments.