The invention discloses a countercurrent type natural ventilation cooling tower cooling capacity evaluation and checking calculation method. The method is characterized in that cooling tower test thermodynamic performance curve and formula are acquired according to the countercurrent type natural ventilation cooling tower performance test data; according to the designed tower inlet air parameters,the designed tower inlet water temperature, the designed tower outlet water temperature and the designed cooling tower thermodynamic performance curve or formula, iterative calculation is performed to obtain the designed gas-water ratio and the designed cooling number, and a correction curve and formula of the tower outlet water temperature to the cooling number and a cooling tower working characteristic curve and formula are obtained; by drawing and calling the designed parameters, the accuracy of the calculation process is checked; according to the design working condition parameters, the tower outlet water temperature and the cooling water temperature difference are calculated under the condition that the designed tower inlet air parameters, the designed tower inlet water temperature and the designed gas-water ratio are corrected with the cooling tower test thermodynamic performance curve obeyed; and comparing with the designed cooling water temperature difference under the designworking condition is performed, and the cooling capacity of the cooling tower is calculated.