A power gear-shifting transmission and an 
engineering machinery are disclosed. The power gear-shifting transmission comprises a 
clutch shaft 
assembly (1). The 
clutch shaft 
assembly (1) comprises a 
clutch shaft (11), a housing gear (12) arranged on the clutch shaft (11), a clutch disc (13) arranged within the housing gear (12), and a gear-shifting 
piston (14) arranged at one end of the clutch disc (13). The gear-shifting 
piston (14) is pushed by a clear hydraulic medium introduced via a 
fluid supply passage (3); the clean hydraulic medium is supplied by a hydraulic 
system (2). The 
engineering machinery comprises the power gear-shifting transmission. Because the power gear-shifting transmission and the 
engineering machinery employ the hydraulic 
system (2) to supply the clear hydraulic medium at stable pressure to the gear-shifting 
piston (14), the shortcomings in the prior art of unclear gear-shifting oil, unstable pressure, bubble content, and air-absorbing tendency are solved, while the advantages of stable gear-shifting and extended service life are provided.