The paper measured leaf area density (LAD), leaf area index (LAI), and diffuse non-interceptance ( DIFN) of Vitex negundo var. heterophylla canopy using LAI-2200 canopy analyzer (PCA), and then analyzed the measured data of three measuring points in five directions. The results showed that: 1) LAD and LAI of the northern part point under canopy were a little greater than those of southern part point under canopy and DIFNs of the two measuring points were both low, suggesting that the canopies had great shielding effect; 2) At the sun light direction at noon time, DIFN of southern part point under canopy was greatest, followed by that of the northern edge point of canopy, and the least was at the northern part point under canopy, indicating that the transmittance of direct solar radiation at the southern part was high though LAI there was great. At the summer solstice, DIFN of the northern edge point of canopy was greatest, followed by the southern part point under canopy, and the least was at the northern part point under canopy; at the vernal equinox and autumnal equinox, DIFN of the southern part point under canopy was greatest, the northern edge point of canopy was in the second place, and the least was at the northern part point under canopy; 3) The result of daily variation of direct solar radiation at the northern edge of V. negundo var. heterophylla showed that: light transmittance at east and west parts were greater, and those at southeast, south, and southwest were roughly the same; around the summer solstice, DIFN at the noon was greater than that in the morning and evening. This paper provides solar direct radiation transmittance measurement method under isolated shrubs canopy, and at the same time it provides the shielding effect at different positions under V. negundo var. heterophylla canopy and sets up scientific basis for determination of appropriate seeding position of afforestation under V. negundo var. heterophylla canopy.