In order to close to the scientific frontier，based on a long plastic scintillator，a new experiment measuring time in magnitude of ns order is established. The experiment is named position - sensitive plastic scintillator spectrometer. The time difference of signals read by both ends of long plastic scintillator can be used to determine the radiation position because the transition path length and time of fluorescent signal in the long plastic scintillator is different when the radiation position is different. The students are required to observe the characteristics of each output signal，and to adjust electronics parameters and temporal relations of two time signals using an oscilloscope，which can help them learn and master how to use oscilloscope in the experiment. It is found that this research experiment is suitable for the senior under - grade students via the teaching practice of three years from 2013 to 2015.