The influence of pulse time delay (PTD) caused by the large-diameter lens on the spatiotemporal characteristics of a broadband laser focal spot is studied to design a high-energy laser system. To this end, diffraction transmission theory of broadband lasers in lenses, which is used in high-energy petawatt laser system with multi-pass amplified structure, is employed. It is found that when the aperture of the broadband laser reaches 360 mm×360 mm, the maximum PTD caused by the lens is approximately 2.5 ps. The spatiotemporal coupling effect peaks when the pulse width is 0.5 ps under the Fourier-transform-limit bandwidth of 3.2 nm and the beam quality is 1 diffraction-limited (DL). The time waveform is distorted, and the focal spot size corresponding to 90% energy concentration is doubled. However, when the compressed pulse width is more than 1 ps or the far-field beam quality is ≥5 DL, the spatiotemporal coupling effect weakens, and the influence of the PTD on focus can be neglected. The research results provide an important theoretical basis for the lens chromatic aberration compensation and fosus performance improvement of domestic high-energy petawatt laser systems.