Objective To find a way to having higher bond strength on mottled enamel. Methods Sixty mottled enamel first bicuspid teeth extracted from fifteen patients needing orthodontic force were prepared and divided into four groups. Group A was routine acid etched, group B was air abraded, group C was etched by clearfil liner selfetching primer, group D was air abraded and then etched by clearfil liner self- etching primer. Next the bond and resin were used. The shear bond strength was observed and compared. The data were analysed by SPSS 11.5 statistical package. Results The shear bonding strength of group A was（2.247±0.261）MPa, group B was（5.374±0.469）MPa, group C was（4.345±0.401）MPa, group D was（5.791±0.636）MPa. The strengths of four groups were significantly different（ P
