This study uses graphs of conductivity measured by a microcomputer-based laboratory (MBL) to promote students’ macro, micro, and symbolic representations when learning about net ionic reactions (NIR). A total of 54 students, aged 14–15 years old participated in this research, and were randomly divided into an experimental group (N= 27) and a control group (N= 27). The students in the experimental group were given graphs of conductivity measured by MBL, while the control group had a demonstration of acid–base titration experiments. The results reveal that the graphs of conductivity have a large effect on students’ macro, micro, and symbolic representations, that is, the students in the experimental group build more representations than the students in the control group.