Background: Caries is common problem found in children. Caries prevalences increased mainly in developing countries such as Indonesia. Theobromine is an alkaloid compound in metilxantin group which can be found in the cocoa bean. Theobromine is believed to prevent caries by restoring the rough surface of email as the result of demineralisation. This research is aimed to analyze the effect of theobromine gel on the surface roughness of deciduous teeth after demineralization. Method: : It was laboratory experiments. Sample of research were 20 incisive cariesfree deciduous teeth. Samples divided into five groups of treatments (concentration of gel theobromine 1%, 2%, 3%, 4%, and 5%). Each group consists of 4 samples. All samples were demineralized with 37% phosphoric acid for 60 seconds. Samples were immersed in artificial saliva for 60 minutes in temperature 37⁰. Roughness examination before and after treatment was conducted using Surface Roughness Tester. Result: This experiment showed that surface roughness is decreasing after treated by five different concentrations of theobromine. There is a significant difference compared to other treatments (p<0,05). Conclusion:Theobromine can be used as one of the caries preventive products. The effective concentration of gel theobromine to decrease surface roughness of teeth email is 5%.