A linear gear shift power transfer mechanism includes a gear shift unit; a power input clamp ring element having an inward-tilted power input ring surface, first teardrop-shaped recesses and first radial positioning hole; a power output clamp ring element having an inward-tilted power output ring surface, second teardrop-shaped recesses and second radial positioning hole; a first ball ring element whose first positioning ring element has a first positioning portion and bulging ring element each provided with limiting slots; a power input rotator having a third teardrop-shaped recesses and first axial positioning hole; a power output rotator having fourth teardrop-shaped recesses and second axial positioning hole; helical resilient elements having radial and axial positioning posts and received in bulging ring elements, with the radial positioning posts disposed in first and second radial positioning holes through the limiting slots, the axial positioning posts disposed in first and second axial positioning holes.