Objective. A case-control study explored the application of case-based teaching methods in the clinical teaching of radiology. Materials and Methods. 126 radiology interns of grade 2018 were selected by cluster sampling and randomly divided into the research group and the control group. The traditional teaching approach was used in the control group and the primary teaching principle was used in the research group. The teaching effects of the two groups were compared. Results. The interns’ test scores, the research group’s case summary multiple-choice questions, case-group multiple-choice questions, case analysis questions, theoretical total scores, and practical operation assessment scores were significantly higher than those of the control group, and the difference was statistically significant (
P
<
0.05
). The total score of dimensions of the interns’ critical thinking ability in the study group were significantly higher than those in the control group, and the difference was statistically significant (
P
<
0.05
). The interns’ perception of teachers, students’ academic self-perception, students’ perception of environment, students’ social self-perception, and the total score of the DREEM scale in the study group were considerably greater than those in the control group, and the difference was statistically significant (
P
<
0.05
). After teaching, the scores of systematic thinking ability and evidence-based thinking ability of the interns were significantly increased. The improvement in the study group was more significant than that in the control group, and the difference was statistically significant (
P
<
0.05
). Following teaching, the scores of learning interest, self-management, plan implementation, and mutual cooperation of the interns in the two groups were significantly upregulated, and the difference was statistically significant (
P
<
0.05
). Among them, the improvement of interns’ abilities in the research group was significantly better than that in the control group, and the difference was statistically significant (
P
<
0.05
). The scores of learning goal, learning process, learning effect, classroom environment construction, teaching strategy, and technology application in the research group were greater than those in the control group, and the difference was statistically significant (
P
<
0.05
). The satisfaction rate of the study group was higher than that of the control group, and the difference was statistically significant (
P
<
0.05
). Conclusion. The application of the case teaching method based on primary teaching principle in the radiology clinical teaching course is helpful to cultivate students’ critical thinking ability and improve students’ performance and classroom teaching effectiveness.