Reserve Replacement Ratio (RRR) has been one of vital marks to scale the development potential of global petroleum companies, which must remain a rational exploration investment proportion. Since 1991, the global increasing exploration investment has driven the reserve, but this goes reverse since 2000. This paper, based on the global oil price, relation between investment proportion and RRR in major petroleum companies, presents that the exploration investment proportion shall be around 20%, which can balance the reserve and mining; if it reaches 25~30% it is very advantageous for petroleum companies to keep a stable RRR and sustainable development, and could lead to an unbalance of reserve and mining if lower than 20%.