The invention relates to a fixed large-bale straw baler comprising a feeding and conveying device, a power driving device, a transmission mechanism, a reciprocating type compressing device, a shredding device, a material precompression chamber, a knotting mechanism, a knotting needle, a compression chamber and a bail discharging part, wherein the feeding and conveying device is connected to a feed inlet at the lower part of the material precompression chamber through the shredding device, a discharge outlet at the upper part of the material precompression chamber is arranged between the reciprocating type compressing device and the compression chamber, the front end and the back end of the compression chamber are respectively arranged on the reciprocating type compressing device and the bail discharging part, materials fed by the material precompression chamber is formed into material bales by the reciprocating type compressing device, the knotting mechanism and the knotting needle are respectively arranged above and below the compression chamber, the knotted material bales are pushed to slide out of the bale discharging part by the reciprocating type compressing device, and the power driving device is respectively connected with the reciprocating type compressing device, the shredding device, the knotting mechanism and the knotting needle through the transmission mechanism. The invention can realize the continuous operation of straw shredding, filling, compression, automatic knotting and automatic bale discharge and replaces manual operation.