This paper discusses the significance of appropriate researchment selection of the sample size, introduces the basic concept and the organizations of the PPS and stratified sample survey, combines with the factors affecting sample size, sampling error, confidence and survey funds, which to design the sample size of the PPS and stratified sample survey. Through the empirical analysis of a large-scale survey of a province, the paper draws the sampling error and confidence can be only considered to the design of the sample size for survey in practice. It also shows that the province adopted 5,000 samples for survey is scientific rationality.