Abstract: Both laser power and microwave power have an important influence on the sensitivity of the diamond nitrogen-vacancy (NV) center ensemble magnetometer based on continuous-wave optically detected magnetic resonance (CW-ODMR) measurement pulse. A set of confocal magnetic field detection system was built based on the ensemble of the diamond NV center. By adjusting the laser power and microwave power, the full width at half maximum (FWHM) and contrast of the corresponding electron spin-resonance (ESR) spectrum could be measured. Experiments indicated that the FWHM of the spectrum was mainly affected by the microwave power, and the spectral contrast was affected by both microwave power and laser power. An obvious light narrowing of the FWHM was observed when the microwave power was constant and the laser power was increased. The optimal parameters of the system can be obtained in two steps. First, adjust the microwave power to get an applicable FWHM of the spectrum. Then increase the laser power to obtain a satisfactory contrast and FWHM of the spectrum.