【Objective】Caucasian clover (Trifolium ambiguum Bieb.) is an excellent nectar source plant, and understanding the morphological characteristics, tissue structure, and development was critical for its reasonable utilization.【Methods】Well-grown standard plants of Caucasian clover were selected and sampled at different developmental periods of the florets, i.e., flower bud visible, petal visible, floret with white petal, floret with pink petal, and floret withered. The paraffin sectioning technology was used to observe the cell and tissue structure of the florets. The starch and soluble sugars including sucrose, fructose, and glucose were determined by capillary aspiration and physiological kit and spectrophotometry at the flower bud visible, petal visible, floret with white petal, floret with pink petal, and floret withered. 【Results】The results showed that: (1) The nectar amount of a individual floret was 0.394±0.095 μL, and the nectar amount per meter square was 4536.93±1319.34 μL. (2) The stamens nectar gland was located at the base of the inner filament of the 9-stamen-combined. The nectar gland tissue had obvious dynamic changes in the starch granules during the whole honey secretion process after PAS staining, which evidenced it was the amyloid nectar gland. (3) The soluble sugar content of floret was the highest at floret with pink petal stage with 7.978 mg/g. Fructose accounted for the largest proportion among the soluble sugar category, peaked at the floret with white petal stage with 66%, decreased gradually after this stage. The starch content accounted for 81%~82% of the total soluble sugar content with a maximum value of 35.173 mg/g at the floret with pink petal stage and the minimum value of 24.168 mg/g at floret with white petal stage. 【Conclusion】The nectar glands of the Caucasus clover belong to the stamens nectar glands, which are composed of secretory epidermal cells and nectar cells. The raw honey is provided by the vascular bundles adjacent to the nectar glands, processed into honey by the nectar gland cells, and finally secreted from the stomata of the epidermis. The soluble sugar content of Caucasus clover florets was the highest in the full flowering stage, and the proportion of fructose was the largest.