Based on the v-t (speed-time) curves in physics, this study analyzes 4 × 100 m relay baton transition period and describes 4 different relay baton transition period v-t state characteristics curves. We can calculate from the curves that the speed of the first three athletes at the moment of transition is above the 96% of the average speed of 100-meter. The research reveals that the ideal v-t curve is a smooth semi-circular curve (without the launching phase). The stability and continuity during the baton transition period are the key factors in 4 × 100 m relay race.