Low mountainous and hilly regions of western Liaoning have a semi-arid climate, are located at the southern edge of Horqin sandy land, and are very vulnerable to soil and water loss. Vitex negundo var. heterophylla, a native species, plays an important role in soil and water conservation; thus, research on the principles of rainfall interception based on the distribution of the Vitex negundo var. heterophylla canopy is crucial. To reveal the variation in rainfall interception of different aged Vitex negundo var. heterophylla canopies, rainfall interception of Vitex negundo var. heterophylla canopies were monitored using artificial rainfall simulation. An empirical model was established. The results showed that there was a significantly positive linear correlation between non-interception by canopies and rainfall rate, with the rate of canopy non-interception decreasing with increasing canopy age. The non-interception rate of the canopy tended to be stable for 250 minutes. Non-interception rates are 91.87% for 1-year-old canopy > 89.75% (2-years old) > 85.08% (3-years old) > 79.00% (4-years old). Non-interception rate and rainfall were significantly positively related. The interception amount of different ages canopies increased with increasing rainfall, and were (5.25±0.49) mm (4-years old) > (3.73±0.65) mm (3-years old) > (2.60±0.23) mm (2-years old) > (1.93±0.55) mm (1-year old) for 250 minutes. Additionally, the interception amount of 1-year old and 2-year-old Vitex negundo var. heterophylla canopies tended to be stable. Canopy interception rates gradually decreased and tended to be stable after 250 minutes; they were 21.00% (4-years old) > 14.92% (3-years old) > 10.25% (2-years old) > 8.13% (1-year old). Additional interception amounts by Vitex negundo var. heterophylla canopies were (0.27±0.03) mm (4-years old) > (0.17±0.04) mm (3-years old) > (0.14±0.01) mm (2-years old) > (0.09±0.02) mm (1-year old). The study revealed the basic principles of rainfall interception by different aged Vitex negundo var. heterophylla canopies, verified the additional interception, and provided a scientific theoretical basis for further study. It is of great significance to the selection of tree species for soil and water conservation and soil erosion control in western Liaoning.