Abstract: The flower bud differentiation and the flowering process of‘Hass’avocado were studied by means of the paraffin section technique and the direct observation method. The results showed that，in Guangzhou，the flower bud differentiation of the terminal shoot of‘Hass’avocado began in mid-late December，which was divided into four stages：inflorescence differentiation，perianth differentiation，stamen differentiation and pistil differentiation. Individual inflorescences differentiated from top to bottom，and apical flowers were the first to complete differentiation. The single flower of‘Haas’avocado has the characteristic of twice flowering，which opens and closes twice within 36 hours，and there is the isomorphism of pistil and stamen. The first flowering time was 6：30–10：30 and 10：30–12：30 was closed. The pistil matured at this stage and had the ability of pollination. The second flowering time was 9：30–14：30 at the next day，14：30–16：40 was closed. At this stage，the filaments elongated，stamens matured and pollinated outward. There is a partial overlap between the two flowering times，and pollination tree varieties can be configured on the basis of the two times of flowering.

Key words: avocado, flower bud differentiation, flowering process