A speedy construction method for the penstock of a large scale hydraulic turbine is provided. The construction sequence thereof is as follows: the spiral case of the hydraulic turbine is installed firstly, then, upwards along the water flow direction, the penstock is arranged in turn from the intake section of the spiral case. The penstock is assembled and welded on a roll welding rack or on a penstock pallet car by use of segments so as to be installed rapidly.