Sources of single-photon in pure quantum states are vital resource fo r quantum information technologies,and have many important application values i n new generation information technology,such as quantum communication and quant um computing.Here,we propose a scheme on the miniaturized and heralded generation of pure singl e-photon through periodically poled lithium niobate (PPLN) crystal.Under the conditio ns of group velocity matching and quasi phase matching,a non-degenerate sponta n eous parametric down-conversion process is designed to generate frequency unco r related photon pairs,thus realizing the preparation of heralded pure state sing le-photon sources.The parameter conditions of frequency uncorrelation are dedu c ed theoretically,and the yield of photon pairs under different conditions are c alculated.It is found that the generation efficiency in the lithium niobate cry stal waveguide structure are 4—6 orders of magnitude higher than that in the correspondin g bulk crystal under the same parameters.These results will be helpful to improv e the purity and the yield of miniaturized single-photon sources,and will p lay an important role in promoting the further development of integrated quantum optical chips.