1, illumination and illumination are necessary conditions for flower bud formation. It has been proved in many fruit trees that shading will lead to the decrease of flower bud differentiation rate. High light intensity (24klx) promoted the flowering of apple within seven weeks after flowering, while low light intensity (12.5klx) decreased the flowering rate, but the decrease of light intensity after seven weeks did not affect the flowering. From mid-June to late July, the flower bud formation of peach increased with the increase of light intensity. The reason why light intensity affects flower bud differentiation may be that light affects the synthesis and distribution of photosynthetic products, and weak light reduces the activity of roots and affects the supply of CTK. The quality of light also affects the formation of flower buds. Ultraviolet rays inhibit growth, passivate IAA, induce ethylene production and promote flower bud differentiation. Apples in high altitude areas grow shorter and bloom easily. 2, temperature, at a suitable temperature, flower buds differentiate more. The flower buds of most deciduous fruit trees begin to differentiate from June to August when the temperature in the northern hemisphere is high. When the high temperature comes earlier than normal, the flower buds begin to differentiate earlier. In fact, each tree species has its own optimum temperature. 3. Water, moderate water stress during flower bud differentiation of fruit trees can promote flower bud differentiation (citrus flower buds begin to differentiate under drought stress), and irrigation is beneficial to the development of flower organs. Moderate drought inhibits vegetative growth, sugar is easy to accumulate, arginine is increased, IAA and GA are decreased, ABA and CTK are relatively increased, which is beneficial to flower bud differentiation. But excessive drought is not conducive to the differentiation and development of flower buds. 4. Soil nutrients, the amount of soil nutrients and the proportion of various mineral elements will affect flower bud differentiation. Nitrogen application during stamen or pistil differentiation of apple can improve ovule vitality. Applying potassium fertilizer can increase the inflorescence of grapes. The flower bud differentiation rate of citrus with nitrogen deficiency decreased with the increase of phosphorus content in leaves.