The aim of this research is to show the differences and interactions between critical thinking skills in students who have a high and low IQ with the discovery learning method. This research was conducted at Senior High School 1 in Baregbeg. The source of research data is all students of class X taking the IPS major. A factorial design was used as the research method. The study used observation, testing, and interview as data collection techniques. Data processing techniques in this study included: data identification, data analysis, normality and homogeneity test, and hypothesis testing. The results of this research is: 1) there are no significant differences in the critical thinking skills of students who have a high and low IQ on economic lessons; 2) the discovery learning method is more effective than conventional method learning to improve critical thinking skills on economic lessons; 3) there is no statistical interaction among learning method, IQ and student’s critical thinking skills.