The relation of forests and water resource is one of the key scientific issues in ecology and hydrology. To understand the spatial heterogeneity of throughfall under forest canopy and determine the suitable number and location of rain gauges for measuring throughfall exactly under the canopy, throughfall was measured under Larix principis-rupprechtii single tree’s canopy during 11 rainfall events, using 32 rain gauges in the growing season (Jun.～Sep.) of 2005. The spatial heterogeneity of leaf area index (LAI) and throughfall ratio was analyzed by statistical and geostatistical method (Semivariance and Kriging interpolation).It indicates that leaf area index (LAI) of canopy has strong spatial heterogeneity at different direction and the LAI reduces with increasing distance from trunk. A negative relation exists between the throughfall ratio and LAI, and the correlative coefficient diminishes with the increase of rainfall. The analysis of semivariance of throughfall shows that the sill C+C0 reduces with increasing rainfall, and the C₀/(C+C₀) and the fractural D increase with increasing rainfall, and D increases firstly and then diminishes with increasing rainfall intensity. These infer that canopy structure is a key factor influencing spatial variation of throughfall ratio when the rainfall is lower; the influence of canopy weakens with increase of rainfall and the distribution of throughfall is random when rainfall is higher. The distribution map of throughfall in different rainfall events produced by Kriging interpolation shows that the lowest region and the highest “funnel" region of throughfall exist, the lowest region of throughfall is situated in the South or southeast direction of canopy, while and the “funnel" region alters frequently in different rainfall events. The comparison of different rain gauge arrangements indicates that the throughfall measued from at least 5 rain gauges (diameter at least 9 cm) at the 1/2 canopy radius can reasonably represent the average throughfall ratio under the Larix principis-rupprechtii canopy.