The present invention relates to the technical field of medicine and pharmacy, and particularly relates to bicyclic group substituted pyrimidine compounds represented by general formula (I), pharmaceutical acceptable salts thereof or stereoisomers thereof, wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are as defined in the specification. The present invention also relates to preparation methods, pharmaceutical formulations, and pharmaceutical compositions of the compounds, and use of the compounds, pharmaceutical formulations, and pharmaceutical compositions for preparing a medicament for treating and/or preventing sexual dysfuntion diseases and diseases with lower urinay tract symptoms.