The rigorous analysis of finite aperture diffractive micro-cylindrical lenses was presented by using a rigorous electromagnetic computational model- the two-dimensional finite-difference time-domain(FDTD) method.Compared with the conventional scalar diffractive theory,the relationship between diffractive efficiency and F-numbers of lenses was analyzed and compared for different incidence polarization waves (TE polarization and TM polarization) and for different profile structures (continuous profiles,8-level profile and 2-level profile).The results show that diffractive efficiency increases with an increasing number of F-numbers and with an increasing number of phase levels,and that the differences between scalar and electromagnetic theory increases with an reducing number of F-number.When F-number is large,diffractive efficiency for TM polarization is a litter larger than that of TE polarization.We believe that these results will be useful to actual applications and academic analysis of diffractive lenses.