Abstract: Using the fruit of Lagerstroemia speciosa as the experimental material to determine the number of seeds produced, seed yield rate, the seed length, width, thickness, thousand seeds mass, and to study the effect of different immersion times, culture temperature, lighting and GA₃ concentration treatment on seed germination. The results showed that the average seeding number of L. speciosa fruit was 89.89±4.09, the average seed yield rate was（34.60±1.27）%, the average length of seeds was（12.21±0.70）mm, the average width was（6.96±021）mm, the average thickness was（1.50±0.15）mm, the mass of thousand seeds was（7.51±0.44）g. The suitable germination conditions were: seed soaking for 24 hours, germination temperature at 30 ℃, light time for 24 hours each day, treatment of GA₃ 200 mg/L, the germination rate and germinatio potential were 80.00% and 63.88%, respectively. GA₃ treatment would have a certain impact on the growth of L. speciosa seedlings, with the increase of concentration, the number of side roots of seedlings gradually decreased, the length of the main root gradually decreased.