There are two entirely different viewpoints about the maturity of condensate oil in the Bozhong 19- 6 condensate field, Bohai Bay basin: mature and highly mature, which have not reached final conclusion. Maturity parameters of light hydrocarbon, saturated hydrocarbon and aromatics are used to comprehensively discriminate the maturity of condensate oil, and the genetic relationship between condensate oil and gas and the formation mechanism of condensate gas reservoir are analyzed. Maturity indexes including isoheptane index and heptane index, Ts/(Ts+Tm) and C29Ts/(C29Ts+C29H), methyl adamantane and methyl diamantane index, MPI, dibenzothiophenes index and TNR2 indicate that the condensate oil in Bozhong 19- 6 gas condensate field is mature. According to the maturity of natural gas and the characteristics of reservoir fluid inclusions, the main condensate accumulation stage is prior to that of natural gas. With charging of vast natural gas in the late stage, the crude oil and natural gas will undergo phase- controlled miscibility to form gas fluid containing liquid hydrocarbons. When the temperature and pressure reach above the dew point of the miscible hydrocarbon system, the condensate gas reservoir will be formed.