In ultrafast high-power laser systems, achromatic lens groups are typically used to replace standard beam expanders to eliminate spatio-temporal coupling (STC) distortions caused by chromatic aberrations. However, alignment errors in these achromatic lens groups can introduce new STC distortions, thereby reducing far-field power density and compromising the desired correction. This paper quantitatively analyzes the STC distortions induced by three types of alignment errors using a broad-spectrum pulse laser transmission model and a thick lens equivalent phase screen model. The impact of these errors on far-field focusing power density is evaluated, and permissible error ranges for each type are established.