Professional courses are the basic carrier of curriculum ideological and political construction. Taking the soil mechanics course of civil engineering as an example, we conduct two teaching experiments on more than 600 undergraduates in two grades, design special teaching plans, conduct a questionnaire survey and an open-ended assignment analysis of students after class. Results show that the second experiment is more successful than the first one. It is necessary to integrate certain ideological and political content in professional courses, but more attention should be paid to the ways and methods of integration. In order to make students gain more in ideological and political contents, teachers are a very important factor. Good teaching effect is not a sufficient condition for good curriculum ideological and political effect, but there is a positive correlation between them. The design of cases should be more in line with the connotation of ideological and political elements. Finally, relevant suggestions from the four dimensions of curriculum, teachers, students and environment are put forward.