AIM: To measure axial length(AL), horizontal and vertical corneal refractive power(K1, K2), anterior chamber depth(ACD)and corneal diameter(white to white)of myopia in college students by IOL-Master(Zeiss Humphrey Systems)and detect the correlation between diopter and all above refractive components. METHODS: The IOL-Master was used in the measurement of the AL, K1, K2, ACD and corneal diameter(white to white)in 1 059 college students(2 118 eyes)with myopia, and AL/CR was calculated. Their diopter was measured by computer refractor. They were divided into three groups according to different mean spherical equivalent diopters: group A of low myopia: < -3.00D(738 eyes), group B of middle myopia: -3.00--6.00D(989 eyes), C group of high myopia: >-6.00D(391 eyes). The SPSS 18.0 was used for the statistical analysis. RESULTS: With the increase of diopter, the AL in myopia eyes was increased and the AL increased significantly in each myopia group(P<0.01); There were statistically significant differences for AL classified with refractive error(P<0.01). There was no significant difference between group A and group B in K1(P>0.05)and there were significant differences among three groups in K2(P<0.05), but there was only significant correlation between K1, K2 and refractive error in middle myopia(P<0.05). The AL was negatively correlated with K1 and K2 in three groups(P<0.01). There was no significant differences between group B and group C in ACD(P>0.05), but there was only significant correlation between ACD and refractive error in low myopia(P<0.01). There was no significant differences of corneal diameter among three groups(P>0.05)and also there was no significant correlation between corneal diameter and refractive error in three groups(P>0.05). AL/CR was 3.183±0.132, the AL/CR ratio was negatively correlated with diopter of myopia(r=-0.761,P=0.000). CONCLUSION: The development of axial length is the main reason in myopia of college students. Middle myopia is induced by both axial length and refractive power. ACD has little effects on diopter of myopia, but corneal diameter has no effects on diopter of myopia.