Fresh Leonurus japonicus powder was prepared with process of squeezing juice from fresh Leonurus japonicus, filtrating, vacuum concentrating at low temperature, and spray drying.Quality of fresh Leonurus japonicus powder was evaluated with concentration of total alkaloids, which was detected with thin layer chromatogram scanning.Effects of three factors, relative d. of herb liquor after vacuum concentration, temperature of cycling water and inlet temperature of spray drying, were investigated.The results of optimal parameters were relative d. of herb liquor 1.04, temperature of cycling water 60°C and inlet temperature of spray drying 175°C.This process was stable and feasible.