The invention discloses a gas sampling and measuring system and method. The gas sampling and measuring system comprises a flow divider, a plurality of sampling points, a heat tracing pipeline and a plurality of single-component gas analyzers. An outlet of the flow divider comprises a plurality of branches. Each sampling point is provided with a gas sampling probe that communicates with a corresponding dilution type gas sampler. Each branch penetrates through the corresponding dilution type gas sampler, each branch is equipped with a Venturi tube nozzle on a tube wall in the dilution type gas sampler, each branch penetrates through the dilution type gas sampler and then is connected with the heat tracing pipeline, and the heat tracing pipeline is connected with the plurality of single-component gas analyzers. According to the invention, the online measurement of the water content in the gas can be realized, the dilution ratios of the dilution type gas samplers are monitored in real time, when a difference between the dilution ratios of the samplers and an inherent dilution ratio exceeds a certain range, an operator can be found and reminded in time to maintain equipment, so that thecontinuous, real and reliable measurement data is guaranteed, and the stable operation of a technological process is guaranteed.