Objective To study the mechanism of arecoline on damage to DNA through the bone marrow cell experiment in vivo. Methods Laser Confocal Microscope was adopted to measure DNA and RNA of the bone marrow cells marked by AO probe. Influences of arecoline on cell cycle were observed by the Flow Cytometer. Results Injection of arecoline to 20, 10, and 5 mg/kg posologic group, the fluorescence pixel ratio apparently higher than that in blank control group of the bone marrow cell inside RNA/DAN, the difference was significant (P