The utility model provides an on - -spot sampling device of seat earth complex body, includes fixed bolster and rotatory sampling device, the fixed bolster includes horizontal fixed operations platform and a plurality of height -adjustable's of the horizontal fixed operations platform of support vertical braces, rotatory sampling device is including installing the power -driven rotation appearance and the sampling device of setting at the horizontal fixed operations platform work end swing joint below and the power -driven rotation appearance on horizontal fixed operations platform, sampling device is including sample support and the sampler barrel of movable mounting in the sample support, sample support below sets up and makes things convenient for the sampler barrel to get the opening of putting to marginal being equipped with along the cutting edge of vertical direction setting in sample support bottom, the sample support is installed at the opening part and to be sealed the horizontal cutting device of open -ended, and this device can have low cost, easy implementation according to planning carrying out the required seat earth complex body sample size adjustment that experimental conditions such as requirement are confirmed after plant species, growth situation, the sample, and when characteristics, the feasibility is high, is worth the large tracts of land to be promoted and implements.