To explore the composition and spatio-temporal dynamics of seed rain in broad-leaved Korean pine (Pinus koraiensis) mixed forest, 150 seed traps were set up in a 25 hm2 broad-leaved Korean pine mixed forest plot in Changbai Mountain. Seeds, fruits, anthotaxy and other in seed traps were collected, identified, and divided into four types, including mature seeds and fruits, immature seeds and fruits, anthotaxy, and others (e.g., seed capsule and seed fragment). They were counted, dried, and weighted by types. From June, 2005 to November, 2006, we collected 47 different types, belonging to 11 families, 12 genus, and 20 species. Total number of seeds and fruits was 121,291, including 23,147 mature seeds and fruits which accounted for 19.1% of the total. Tilia amurensis and Fraxinus mandshurica, two species with the most seeds and fruits, accounted for 90% of the total. Seasonal dynamics of seed rain from May 2006 to November 2006 were analyzed. We found that: there were the most number of seeds and fruits between 15 July and 25 October, but it was composed of immature seeds and fruits. In the middle of October, mature seeds and fruits reached their peak, but immature seeds and fruits still accounted for high proportion. When analyzing the number of mature seeds and fruits in each seed trap, there were 91 traps that contained 100-200 mature seeds and fruits, and 1 trap without any mature seed or fruit. When looking at the number of species in each seed trap, 7 species were the maximum species found in a trap, and usually 3 or 4 species were found in most of the traps. The spatial patterns of mature seeds and fruits of 6 dominant species were analyzed. We found that: mature seeds and fruits of Tilia amurensis and Fraxinus mandshurica distributed in the whole plot, while Ulmus japonica、T. mandshurica、Acer mono and A. pseudo-sieboldianum distributed in some parts of the plot. There were significant relationships between spatial patterns of mature seeds and fruits, and their parent trees, indicating that their mature seeds and fruits were not dispersed far from their parent trees.