The invention provides a synthesis gas washer and a synthesis gas washing system. The synthesis gas washer comprises a synthesis gas pipe and a grey water pipe, wherein a water spraying nozzle of the grey water pipe is communicated with the synthesis gas pipe, a sleeve is arranged in the synthesis gas pipe, the water spraying nozzle of the grey water pipe is opposite to the gas inlet of the sleeve, and a swirler is arranged at the position, close to the water spraying nozzle of the grey water pipe, of the grey water pipe. The swirler is arranged at the position, close to the water spraying nozzle of the grey water pipe, of the grey water pipe, initial atomization can be conducted on wash water through the swirler, the contact areas between the dust particles and atomized droplets are enlarged, the atomized droplets can rapidly wrap the dust particles and can be sprayed out at a high speed, and therefore particle separation and gas purification can be better achieved through the synthesis gas washer.