Spontaneous parametric down-conversion (SPDC) is a primary method for preparing quantum light sources. In this paper, the central technical schemes of different types of SPDC (type-0, type-Ⅰ, type-Ⅱ) were introduced, and the research progress and applications of quantum light sources to prepare multi-photon quantum entangled states and high-dimensional quantum entangled states were discusseed. At the same time, the preparation and application of narrow linewidth entangled states from cavity-enhanced SPDC were also introduced. Finally, the existing problems and future development direction of various schemes were analyzed and prospected.