The invention discloses a low-NOx combustion and white smoke decreasing coupling power station system and methods. The low-NOx combustion and white smoke decreasing coupling power station system comprises a high-temperature strong reducing combustion system, an air separation system, a liquid oxygen condensing system, a smoke condensate recovery system and a smoke re-heating white smoke decreasing system. Pure oxygen is obtained through an air separation device, then the pure oxygen is delivered into a main combustion area through an auxiliary wall type air spraying opening, the excessive oxygen coefficient of the main combustion area is controlled to be between 0.5 and 0.8, a high-temperature main combustion area with strong high-oxygen-concentration reducing property is created, and NOx emission is greatly reduced while the fuel combustion characteristic is improved. Cold energy of liquid oxygen is utilized, the smoke temperature before an electrostatic dust collector is lowered, the efficiency of the electrostatic dust collector is improved, moisture in the smoke is recovered through a smoke condensing system, and meanwhile white smoke decreasing is achieved. Liquid oxygen residuals are exhausted through a large-temperature-difference phase change heat exchange condensing steam turbine, circulating cooling water of a power plant is reduced or omitted, meanwhile the oxygen temperature is increased, efficient utilization of low-grade heat is achieved, and the economical and environment-friendly benefits of the power plant are improved remarkably.