The invention provides a preparation method of an organic fertilizer for a bamboo forest. According to the method, plant litter is selected to acquire a nutrient solution, dominant bacteria of a plant litter layer are acquired after the separation, purification, culturing and breeding processes of bacteria, the acquired dominant bacteria are inoculated into compost prepared from the plant litter to be fermented, and the organic fertilizer for the forest is obtained. With the adoption of the organic fertilizer for the bamboo forest, the physical structure of soil can be changed, soil hardening can be improved, moisture and fertility are preserved, the soil fertility is improved, the number of beneficial microorganisms in soil is increased, harmful infectious microbes in the soil are killed, and accordingly, growth of root systems of bamboo is promoted. The invention further provides a use method of the organic fertilizer for the bamboo forest. With the adoption of the use method of the organic fertilizer for the bamboo forest, the bamboo shooting rate of the bamboo forest can be increased by 27.5%, the bamboo rate is increased by 10%, and the growth speed of young bamboo is increased by 15%.