Technology, pedagogy, and content knowledge (TPACK) has been considered as a promising theoretical framework to guide teacher educators in designing and developing in-service K12 teacher education programs. However, it seems unclear whether in-service teachers have different TPACK perceptions when entering the education programs. This study surveyed the TPACK perceptions of 2,728 Chinese in-service K12 teachers. A questionnaire adapted from Koh, Chai, and Tsai's survey was validated by reliability and validity tests. Exploratory factor analysis revealed that Chinese in-service K12 teacher's TPACK perceptions could be grouped into five scales. Analyses of means and standard deviation of all the variables of the TPACK construct to examine Chinese in-service K12 teachers' TPACK perceptions showed that teachers had rated themselves as slightly above five points for all the variables. Independent sample t tests to examine the relationships between in-service K12 teachers' gender and the TPACK variables indicated that male teachers rated themselves higher than female teachers for the variable content knowledge (CK) and lower for the variable pedagogical content knowledge. F tests to examine the relationships between in-service K12 teachers' years of service and the TPACK variables revealed that young in-service K12 teachers tended to perceive better in the capacities of applying technology and worse in the capacities of teaching method and subject matter. Hierarchical regression analysis to explore which variables (technological knowledge, pedagogical knowledge, CK, pedagogical content knowledge, technological content knowledge, and technological pedagogical knowledge) could predict the variable of TPACK showed that in-service K12 teachers' perceptions of pedagogical knowledge, technological knowledge, and CK had the largest positive effect on the TPACK variable.