In　order　to　improve　the　safety　level　of　two-lane　highways　in　mountainous　areas,　this　paper　investigated　the　relationship　between　highway　geometric　features　and　rear-end　crash　accidents.　By　using　negative　binomial　generalized　models　and　separating　the　139　kilometers　highway　segment　into　94　successive　vertical　slope　units,　the　statistical　software　Stata　9.0　was　used　to　evaluate　the　effects　of　8　variables　which　were　based　on　roadway　geometric　characteristics　of　the　accidents　of　rear-end　crashes　occurred　from　2003　to　2005　on　the　mountainous　two-lane　highway　in　Gansu　Province.　The　variables　which　influence　the　accidents　of　rear-end　crashes　significantly　was　accumulated　by　vertical　slope　length.　The　results　suggest　that　there　are　strong　positive　relationship　between　the　accidents　of　rear-end　crashes　and　accumulated　vertical　length.　Therefore　avoiding　long　vertical　length　as　much　as　possible　in　highway　design　is　suggested.