The probe field gain and its relation with the population rule in high level in the quasiΛtype fourlevel atom system interacting with two light fields at low-light levels under stable state are numerically investigated. It is found that, even for low-light level, with the variation of probe field and the relevant frequency dteuning of interlevel transition, the system always displays three gain peaks for probe field simultaneously and two fixed positions where the electromagnetically induced transparency (EIT) is observed, when all phases of Rabi frequencies are zero. When the system displays EIT, the probe field related population in the high level is zero. When the phase of Rabi frequency is changed, gain and absorption for the probe field occur, EIT phenomenon also exists, but the phase change cannot influence the population in the high level alone. It is worth noting that all results are achieved without any approximation.