The topic 'photosynthesis' contains many intangible and abstract scientific concepts, regarding which students hold many preconceptions. Conceptual learning is a process of co-creation and flow that requires the teachers' higher educational level on conceptual teaching. The present research considers photosynthesis as an example. Results of Ball's 2008 research on teachers' content knowledge for teaching served as the theoretical framework. In total, 30 biology teachers from 11 lower-middle schools in a medium-sized city in China were selected as the research objects. The conceptual learning achievements of 1442 students taught by those teachers were used as a yardstick, and two sets of self-designed questionnaires were used to demonstrate, describe, and discuss these elements and their current state in the teachers' mind and determine influencing factors. According to the results, except for the knowledge of concept and student element, all the other three elements attained the passing level. Specifically, the level of common concept knowledge was relatively high, but this element had not attained the perfect level. A scope for improvement was observed for the other three conceptual knowledge elements. No significant difference in the knowledge elements level was observed among the teachers from different schools.