Abstract: The holographic modal wavefront sensor is a novel sensor, which directly detects the aberration modes included in the distorted wavefront by employing a multiplexed computer-generated holographic element (MCGHE). This element can be designed and generated by pre-coding multiple Zernike aberration modes. We propose an efficient approach of designing the MCGHE, which is generated through superposing several amplitude gratings distorted by specific aberration modes. The analytical formulas are derived to characterize the relationship between the sensor output signal and the coefficient of particular Zernike aberration mode，given the condition of small aberration approximation. The MCGHE is designed and simulated in detecting single Zernike aberration mode or multiple ones. The demonstration experiment is carried out by utilizing a liquid crystal light valve. The experimental results are consistent with the numerical ones to some extent.