Abstract: 【Objective】To clarify the grain traits and accumulation rule of nutrient components during the growth and development of calabash-seed.【Methods】The variety “Jindi No.3” （Breeding by Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences） was used as the test material. The grain size,weight and crude fat,protein,starch,soluble sugar of the grains were studied after 7 to 70 days of pollination.【Results】There was a great difference in grain traits and nutrient content at different growth stages. The first 14 days after pollination was the rapid growth period of the grain,and the seed morphology was mainly established in this stage. The length and width of the grains increased from 0.91 and 0.51 cm to 1.76 and 1.11 cm,and the increase amount accounted for 44.54% and 52.54% of the grain after completion. Fourteen days after pollination,grain size increased slowly,but the grain weight increased continuously until the grain was mature. From 14 to 70 days after pollination,grain length and width increased by 8.56% and 3.30% respectively. Grain weight per melon increased from 11.52 g to 67.31 g;the dry weight of 100-grain increased from 3.77 g to 20.93 g. During seed maturation,crude fat and protein contents increased gradually,and reached the highest values on 63^rd and 70^th day after pollination,which were 43.21% and 35.07%. Starch content and soluble sugar content decreased gradually on 28^th and 14^th day after pollination,respectively,and soluble sugar content could not be detected on 56^th day after pollination.【Conclusion】Seed maturation of calabash-seed divided into two stages：the first stage was the main stage of seed morphology formation within 14 days after pollination;the second stage was the accumulation stage of crude fat and protein at 21 days after pollination. The critical period for the accumulation of grain nutrients from 28 to 42 days after pollination.

Key words: Calabash-seed, Grain traits, Nutrient composition, Accumulation rule