The　determination　of　evidence　weights　is　an　important　step　in　evidence　combination,　which　significantly　influences　final　results.　Taking　into　account　the　assumption　of　＂psychology　of　economic　man＂,　decision-makers　may　tend　to　seek　similar　pieces　of　evidence　to　support　their　own　evidence　in　the　process　of　negotiation　and　thereby　forming　an　alliance　of　benefit.　In　the　process　of　negotiation,　decision-makers　are　concerned　about　the　fairness　of　negotiation.　To　achieve　the　aim　of　fairness,　in　this　paper,　we　extend　the　concept　of　evidential　reasoning　(ER)　to　evidential　reasoning　based　on　Gini　coefficient　(ERBGC)　to　obtain　the　weights　of　evidence.　The　main　concept　of　the　ERBGC　approach　is　that　the　decision-maker　is　willing　to　engage　negotiation　with　others　only　when　the　negotiation　process　is　fair,　that　means　the　gap　between　maximum　and　minimum　distributed　interests　among　all　decision-makers　is　less　than　that　without　negotiation.　It　shows　that　negotiation　can　make　interests　distribution　fairer　among　decision-makers.　In　this　study,　the　optimization　model　was　developed　to　generate　the　relative　weights　based　on　Gini　coefficient　and　enable　weighted　evidence　to　be　combined　using　the　ER　rule.　The　approach　is　then　applied　to　a　case　study　and　compared　with　other　related　approaches　to　demonstrate　the　effectiveness　and　applicability.