Objective To understand the changing trends of the incidence of sexual behaviors among Chinese college students in the past 30 years and the influencing factors

so as to provide a reference for ensuring college students to establish correct sexual concepts and attitudes and engage in safe sexual behaviors.Methods Λ crosstemporal meta-analysis was conducted on data from 167 surveys on the occurrence of sexual behaviors among college students during 1990-2018.Results Since 1990

the incidence of sexual behavior among college students in China has shown an increasing trend

from 8.88 % in 1990-1999 to 17.80% in 2011-2016.Using time as the independent variable and the incidence of sexual behavior among college students as the dependent variable

correlation and regression analyses were conducted

and the results show that the function between the incidence of sexual behavior and time among college students was y=-1 116.589+0.563 x（P<0.05）

and the explanatory power of time on the incidence of sexual behavior was 47.8%.The incidence of sexual behavior among male college students showed a significant increa sing trend

while the incidence of sexual behavior among female college students showed a trend of "increasing first

then decreasing".The results of the correlation and regression analysis showed that the function between the incidence of sexual behavior and time for male college students was y=-1 857.235+0.935 x（P<0.05） and that for female college students was y=-574.410+0.291 x（P<0.05）

and the explanatory power of the model was 72.1 % and 25.3 % for males and females respectively.The incidence of sexual behavior among college students in the east

central and west regions all showed an overall increasing trend with time.The results of correlation and regression analysis showed that the incidence of college students’ sexual behavior in the central region was most significantly affected by time

as the function between the incidence of college.students’ sexual behavior and time was y=-1 905.787+0.956 x（P<0.05）

and the explanatory power of time on the incidence of sexual behavior reached 59.2%;the function between the incidence of college students’ sexual behavior and time in the eastern region was y=-870.010+0.440 x（P <0.05）

and the explanatory power of time on the incidence of sexual behavior was 33.7%;although the incidence of sexual behavior among college students in the western region changed over time

the time effect was not statistically significant（P>0.05）.Conclusion Early pubertal development of adolescents and postponement of marriage age

improvement of economic conditions and popularity of the Internet are as sociated with the increase of the incidence of sexual behavior among college students.Therefore

it is recommended to change the traditional concept and carry out family sex education at the right time

to improve the sex education curriculum and assign a key role to the school

and to strengthen the supervision of the Internet and carry out Internet science education

thus guiding college students to establish correct sexual concepts and attitudes and engage in safe sexual behavior.