Abstract: The speed of β-ray in the air is measured by the coincidence of two plastic scintillator detectors using 90Sr-90Y β source.A comparison between theoretical value and the experimental value revised by Casino software considering energy loss is presented.It is shown that the two values are in agreement with each other well.The result provides an experimental evidence for theoretical values of β-ray speed,and it is proved that our equipment and experimental design are effective.

Key words: scintillator detectors, 90Sr-90Y β source, β-ray, electron speed