The invention provides an on-site splicing method of a bottom-basket system of a deck erection crane of a cable-stayed bridge, which is suitable for erection of a bottom-basket system matching the deck erection crane on a main beam 0#. The method comprises the following steps: installing a bottom basket longitudinal beam, hoisting the sectionally-spliced longitudinal beam below the front end of amain beam 0# block, suspending the front end of the longitudinal beam at the front end of the deck erection crane and hanging the back end of the longitudinal beam upside down in a sliding manner to atrack in the transverse direction of a bridge; installing a middle transverse beam, moving the middle transverse beam out of the front end of the main beam 0# block by the deck erection crane after the middle transverse beam is finished sectionally splicing, putting down the middle transverse beam after horizontally rotating the middle transverse beam till the middle transverse beam stretches across two longitudinal beams which are installed in places and fixedly connecting the middle transverse beam with the middle part of the longitudinal beam, and orderly finishing processes of a front transverse beam and a back transverse beam according to the installation process of the middle transverse beam. The deck erection crane is utilized for splicing all rod parts of the bottom basket and hoisting the rod parts so that the problem of wholly splicing the bottom basket system due to the limited place is resolved.