Screening of native oil recovery functional microorganisms in reservoirs and exploring their oil recovery mechanisms, conducting in-situ test of microbial enhanced oil recovery (MEOR) to evaluate their feasibility in high-salinity reservoirs. Functional bacteria were screened by crude oil plate, their adaptability to high high-salinity environment was evaluated, and cultivation parameters were optimized. The oil recovery potential was analyzed and the oil recovery mechanism was explored by surface tension, emulsification property, viscosity reduction and wax resistance, and four components. The microbial oil recovery preparations were produced and prepared, and field tests of MEOR were conducted in high-salinity reservoirs to evaluate their field application efficiency. The results showed that Bacillus velezensis YD1 could grow and reproduce at a salinity of 140,000 mg/L, pH = 6–9, 25–45 °C. The surface tension of the supernatant was 28.44 mN/m, EI24 was 100%, the wax resistance rate was 80.79%, and the viscosity reduction rate > 80%. The content of wax, resin, and asphaltene decreased by 10.59%, 3.79%, and 2.36%, respectively. The content of saturated hydrocarbons and aromatic hydrocarbons increased by 5.50% and 0.68%, respectively. The relative content of hydrocarbons (C16–C40) and hydrocarbons (C20–C40) decreased by 3.03% and 3.43%, respectively. The solidification point and wax precipitation temperature of the treated crude oil decreased by 5.7 °C and 3.0 °C, respectively. The physical simulation flooding showed that the oil recovery rate increased by at least 10%. Four well-times single well huff-puff and six well-times wax removal were carried out in the field test, with an average extension of the well washing cycle by 50 days and 45 days, with a cumulative oil increase of 756.45 t and 579.80 t, respectively. Therefore, the native B. velezensis YD1 has practical value in the field application of high-salinity reservoirs, which lays a theoretical foundation and provides technical support for the promotion of biological oil recovery technology system in high-salinity reservoirs.