Abstract:Collection of data of phenotype and cytology were collected from 2013 to 2015,including data of photosynthetic factor.Cultivar of Jingu 21 and its autotetraploid are materials of this experimen,We compared them by morphological observation,and ploidy examination is from cytological observation.On the basis of physiological and biochemical characteristics,?experimen study about photosynthetic factor response for diurnal variation of different ploidy.?It turned out that:compared with millet of diploid,tetraploid increased leaf width by 6.11%,increased index of leaf shape from 11.82 to 9.25,increased length of diameter of main stem by 13.04%,increased length of diameter of main?panicle by 5.39%,increased thousand seed weight by 46.16%,decreased leaf length by 17.01%,decreased length of main stem length by 23.29%,decreased length of main panicle length by 5.45%,decreased?panicle?weight by 24.42%,decreased grain?weight?per panicle by 62.47%,decreased fruiting rate by 47.30%.The?results?of?the?microscopy scanning showed that tetraploids had long growth period,globular ovaries,?crenated stigmas,big pollen,some of which are wizened.In addition to these,their seeds have low germination percentage,and their synthetic amounts of chlorophyll and N are small at booting stage.Compared with its tetraploid,photosynthesis factors of diploid affect each other are more sensitive.Unbalance of sink and source is main impact factor to low photosynthetic rate of autotetraploid of induced strains at booting stage.Phenotype of tetraploid is the embodiment of interaction between different genomes,and there must be a rebalancing in its evolution.