Abstract: In this pepar have analysed and studied the variation of the debris population in low Earth orbit with the solar radiation flux F 10 7 .A calculation method to predict the long periodic variation of solar flux F 10 7 and a mathematics model to predict space debris population have been derived.The results show that:①The strong solar activity significantly accelerated the decay of satellites and debris in low Earth orbit.As a result,the yearly mean growth rates of the debris population decline;②The variation of the space debris population relates with ll year variation of the solar activity.The correlation coefficient reaches 0 9 during the 21th and 22st solar activity cycles from 1974 to 1994;③The space debris population increases with the launch rate.The debris having sizes of 10 cm or larger increase at about double the rate of growth of the cumulative launches; ④By 2020 the population of tracked objects(>10 cm in diameter)will reach 14500 when launch rates are fairly constant,being 114.264;⑤If untracked debris(1～10 cm in diameter)population will increase at about double the rate of growth of the trackable population,the space debris population will reaches 125000 by the year 2020.