The Larix principis-rupprechtii plantation, which is the dominant forest type in Saihanba, Hebei Province, accounts for 70.6% of the total forest area. However, natural regeneration in the L. principis-rupprechtii plantation is extremely poor due to the low seedling and sapling recruitment rate. Exploring the limiting factors that affect the natural regeneration and growth of L. principis-rupprechtii seedlings in stands of different ages is not only urgent but also important for forest management and natural resource conservation. In this study, we conducted a field vegetation survey and collected environmental samples (soil and litter) from 18 plots (50 m × 50 m) of two age classes (Ⅲ age class, 20-30 year-old stand; Ⅳ age class, 40-30 year-old stand). Redundancy analysis (RDA) and partial RDA were applied to study the relationship between the density of naturally recruited seedlings and environmental factors, and the relative importance of soil-litter and stand structure factors, respectively. Our objective was to answer the following questions: (1) What is the dominant factor affecting natural regeneration in the L. principis-rupprechtii plantation? (2) Are there any differences in factors affecting the natural regeneration of L. principis-rupprechtii in two stands of different ages? (3) Is there any change in the relative importance among environmental factors affecting the growth of L. principis-rupprechtii seedlings in different growth stages? Our results showed that: (1) soil-litter factors played a dominant role in the natural regeneration of L. principis-rupprechtii. The total variance explained by soil physical-chemical properties and litter was more than 55%. On the contrary, the effect of pure stand structure was relatively weak; (2) the dominant factors that affect the natural regeneration of L. principis-rupprechtii in stands of two age classes were different. For stands of the Ⅲ age class, the main factors affecting stand regeneration were the stand density, soil organic matter, soil available P, soil alkali-hydrolyzed N, and the thickness of litter. However, the thickness of litter, soil total K content, soil pH, stand density, and basal area were the main factors hindering natural regeneration in stands of the Ⅳ age class. Variation in the relative importance of factors between two age class stands was mainly due to the high density and low survival rate of seedlings. The death rate of seedlings < 5 cm in height was 94% and 70% in stands of the Ⅲ age class and the Ⅳ age class, respectively; (3) the growth of seedlings was mainly affected by soil-litter factors during the earlier growth stage, while the stand structure gradually became the critical factor. However, this tendency was not obvious in the stands of the Ⅳ age class. The stand structure variables (except for the basal area) were positively correlated with the seedlings across five-height levels. Our results reveal the critical factors that affect the natural regeneration of the L. principis-rupprechtii plantation, and provide a theoretical foundation for improving the natural regeneration as well as ameliorating stand structure.