This study aims to describe the implementation of pedagogical content knowledge (PCK) of mathematics teachers in the teaching practice of the material system of linear equations of two variables (SLETV). The approach used is a qualitative case study. The main instrument is the researchers themselves and the supporting instruments is a vignette sheet, sheet Content Representation (CoRe), and video tape recorders (Handycam). Research procedure includes providing vignette sheets and sheets of CoRe, making instructional videos and conducting the interview. Data were analyzed using frameworks Karahasan. The results showed that the subject 1 (S1) found that the implementation of the PCK S1 when teaching increased from PCK S1 prior to the implementation of the teaching practice, while the subject 2 (S2) found that the implementation of the PCK S2 upon teaching declined from PCK S2 prior to the implementation of the teaching practice.