For being convenient for the design, improvement and use of pile clamping mechanism of hydraulic static pile driver, the static forces of pile clamping mechanism and prefabricated pile were researched and analyzed under pile driving; the contact between prefabricated pile and pile clamping jaws under pile driving was investigated. The equation of the maximum transmission pile driving force of pile clamping mechanism of hydraulic static pile driver was obtained. After studying and analyzing the equation, it was revealed that the maximum transmission pile driving force of pile clamping mechanism of hydraulic static pile driver is augmenting under pile driving by adding the distribution number of pile clamping mechanism in each layer, the number of contact surfaces between prefabricated pile and pile clamping jaws, static friction coefficient between upper, nether pile clamping jaw and prefabricated pile and oil pressure of pile clamping cylinder.