A vibration extrusion type water chestnut harvester was designed to solve the problems of high manual labor intensity， low operation efficiency， and difficulty in separating fruit and soil during dry harvesting of water chestnuts. The separated water chestnuts were scattered on the surface for easy manual picking by enhancing the effect of crushing the soil layer and improving the degree of fruit and soil separation. The key parameters affecting the separation performance were determined to be the amplitude of the vibration plate， the vibration frequency of the vibration plate， and the speed of the nail roller by analyzing the stress on the water chestnut soil block during the process of operation. The range of key parameter values was preliminarily determined according to the existing experience. Design-Expert 10.0 was used to design the CCD center combination test by using the amplitude of the vibration plate， the vibration frequency of the vibration plate， and the speed of the nail roller as the influencing factors， and the rate of soil fragmentation as the evaluation index. The results of simulating the RecurDyn-EDM coupling showed that there was a better crushing effect and the rate of soil fragmentation was 93.58% when the vibration frequency of the vibration extrusion plate， the vibration frequency of the vibration plate， and the speed of the nail roller was 33.04 mm， 6.63 Hz， and 336.72 r/min， respectively. The results of field verification test showed that the actual rate of soil fragmentation， the rate of water chestnut， and the damage rate was 93.54%， 80.33%， and 28.08%， respectively when the actual amplitude of vibration plate， vibration frequency and the speed of nail tooth was 32.41 mm， 6.5 Hz， and 330 r/min， respectively. It is indicated that the effect of crushing soil is good， and the fitting degree with the results of simulation is high.