The Standard Penetration Test (SPT) is widely used as an in-situ investigation method in geotechnical engineering in the world although the measured N-value (NF) in the field is affected by many factors due to energy losses. This paper investigates the real-time motions of the SPT hammeranvil during SPT and their effects on impact energy. The real-time hammer and anvil motions are monitored using a high-speed Digital Line-Scan Camera (DLSC) and stress waves are measured using a Pile Driving Analyzer (PDA) during SPT with a donut hammer and rope-pulley system. It is found that two types of the hammer-anvil motion exist; recontact and restrike of the hammer-anvil after primary impact are observed, depending on the soil resistance. The recontact contributes to the maximum impact energy and the sampler penetration while the restrike has no effect on either of these. Dominance of the hammer-anvil motion transits from recontact to restrike as the penetration resistance of the ground increases.