A spin-exchange relaxation free (SERF) rubidium atom magnetometer is developed for liquid-state zero-field nuclear magnetic resonance detection. The magnetic resonance curve of the atom is measured by the experiment. It is verified that the magnetometer is working at the status of SERF, and the result is consistent with the theory. Using the method of increasing the intensity of light, the bandwidth of the magnetometer is improved, and the bandwidth demand of the liquid zero field nuclear magnetic resonance is met. The sensitivity of the magnetometer in the frequency range of 20~300 Hz is lower than 18 fT/Hz1/2. A liquid-status zero-filed nuclear magnetic resonance device based on magnetometer is used to measure the the sample of formic acid, and zero-filed nuclear magnetic resonance spectra of formic acid marked by 13C is got. Which verifies the usability of magnetometer.