The rationales behind design are dissimilar to those behind art. Establishing an adequate theoretical foundation for conducting design education can facilitate scientising design methods. Thus, from the perspectives of the semiotic theories proposed by Saussure and Peirce, we investigated graphic design curricula by performing teaching experiments, verifying the adequacy of applying these theories to poster design. During the teaching experiment, a matched groups design method was used for assigning 30 students to either an experimental group or a control group. The results of the experiment revealed that compared with the control group students, the experimental group students, who applied the semiotic theories to their poster designs, performed more favourably in image creativity, picture aesthetic, typography, and total poster design score. The posters created by the students were submitted to International Triennial of Ecological Posters "the 4th Block", and a total of 4 creations from the experimental group were accepted. The results of the teaching experiment verify that applying semiotic theories to graphic design curricula facilitates improving student ability to observe objects and cultivating their capability to design posters and reinforce the visual tension in the posters