The invention discloses a process for producing gas-phase natural gas and liquid-phase natural gas through nitrogen-methane separation in nitrogen-containing natural gas. A target product is natural gas or liquefied natural gas. According to the nitrogen-containing natural gas nitrogen-methane separation process, the gas on the top of the tower is compressed, the compressed tower top gas serves as a heat source of a bottom reboiler, a rectifying tower top condenser and the bottom reboiler are coupled to form a heat exchanger, a low-grade cold-flow condensing tower top product of the tower bottom is utilized, and the aims of saving the energy and reducing the consumption are fulfilled. The basic nitrogen-methane separation process comprises the following steps of: precooling raw material natural gas, rectifying tower separation, tower top gas-phase compression, reheating the tower top product and extracting and reheating the tower bottom product. The process has the characteristics of wide raw material natural gas application range, high methane recovery rate, low energy consumption and low equipment investment.