The invention relates to a pin shaft supporting seat part capable of sliding during construction and rotating during using, a pin shaft supporting seat and a spatial structural system thereof. The pinshaft supporting seat part comprises a lug plate provided with a pin shaft hole, a rotating piece, a base provided with a first limiting clamping slot, a guiding rail provided with a second limitingclamping slot and a pre-buried plate. The rotating piece is connected to the bottom of the lug plate, and the lower portion of the rotating piece can be rotatably arranged in the first limiting clamping slot of the base. The base is slidably arranged in the second limiting clamping slot of the siding rail. The pre-buried plate is arranged at the bottom of the sliding rail. Through the arrangement,the contradiction of stress of a traditional pin shaft supporting seat can be overcome, the horizontal thrust generated by the structural weight can be released after the supporting seat is installed, the stress is reasonable, the processing is convenient, complex stress conditions can be adopted, and the needs of building modeling can be better met.