To make the directional demolition of the cooling tower safer and more controllable, the axial force calculation method of the retained columns of the cooling tower is proposed. Firstly, in the light of the similarity relationship of the force, the relationship between the axial and Z-direction force of the column was investigated. Based on the plane section assumption, the calculation formula of the Z-direction force of the retained columns was deduced. Then, the effects of 5 parameters, specifically the elastic modulus of the ring beam and the column, the height of the column, the number of retained columns and the central angle corresponding to the top of the adjacent column on the Z-direction force of the retained column were explored by FEM. The calculation formula of the Z-direction force of the retained column was modified according to the results of FEM, and the applicability of the modified formula was studied. The results show that the blasted cooling towers do not satisfy the assumption of plane section on all retained columns. In practical engineering, the above 5 parameters do not affect the distribution characteristics of the Z-direction force of the retained columns: the distribution of the Z-direction force along the y-axis direction is always ′compression at both ends and tension in the middle′, the maximum compression in the retained columns always appears on the n row, with the maximum tension always on the (n-4) row. When the blasting center angle is in 200°-240°, the relative error of the modified formula is within 21%, and the modified formula exhibits good applicability in different cooling towers. The calculation formulas of axial force of retained column provide theoretical supports for the demolition of cooling tower from the perspective of mechanics, improving the safety of directional demolition of cooling tower.