A built-in sliding plug door for rail vehicle, comprising a control mechanism, a driving mechanism, a bearing mechanism, a pressing mechanism, a guiding slide channel, a side wall portion, a door leaf and a vehicle body, wherein: the bearing mechanism comprises two guiding posts fixed to the vehicle body, two sleeves, a connecting rod, a slide block and a guiding roller, wherein the top of the slide block is fixedly connected to the door leaf, the bottom of the slide block is connected to the driving mechanism, the slide block is fitted on the connecting rod and can move along the connecting rod in the transverse direction, the two sleeves are fixed to the two ends of the connecting rod respectively, the sleeves are fitted on the guiding posts and can move along the guiding posts in the longitudinal direction, the guiding roller is fixed to the slide block and the guiding roller is arranged in the guiding slide channel and the guiding roller works together with the guiding slide channel; the control mechanism is connected to the driving mechanism and the pressing mechanism respectively; the side wall partition is arranged in the inner side of the vehicle body, and an interlayer is formed between the side wall partition and the vehicle body, and the size of the interlayer matches the side of the door leaf; the control mechanism, driving mechanism, bearing mechanism, pressing mechanism, and guiding slide channel are arranged in the inner side of the vehicle body; the guiding slide channel comprises a linear channel section and a curved channel section, wherein, the linear channel section is arranged in the transverse direction, the curved channel section is arranged in the longitudinal direction, the bottom of the curved channel section is connected with the linear channel section, and the top of the curved channel section is close to the door leaf, wherein the built-in sliding plug door further comprises a sealing mechanism, characterized in that the linear channel section is perpendicular to the curved channel section and is arranged such that when the guiding roller is located in the linear channel section, the door leaf is located at the inner side of the vehicle body; and the curved channel section is arranged such that when the guiding roller is located at the top of the curved channel section, the door leaf is flush to the outer side of the vehicle body, wherein the slide block has a base, a sliding rod, and an inclined groove, the base is arranged on the bottom of the slide block, and the base is connected to the driving mechanism; one end of the sliding rod is fixed to the base, and the other end of the sliding rod is arranged in the inclined groove; the inclined groove is arranged on the slide block, wherein the sealing mechanism is arranged on the outer periphery of the door leaf; and a seal processing is carried out between the sealing mechanism and the door leaf during the closure of the door, under the pressure of the pressing mechanism. the bearing mechanism comprises two guiding posts fixed to the vehicle body, two sleeves, a connecting rod, a slide block and a guiding roller, wherein the top of the slide block is fixedly connected to the door leaf, the bottom of the slide block is connected to the driving mechanism, the slide block is fitted on the connecting rod and can move along the connecting rod in the transverse direction, the two sleeves are fixed to the two ends of the connecting rod respectively, the sleeves are fitted on the guiding posts and can move along the guiding posts in the longitudinal direction, the guiding roller is fixed to the slide block