The dynamic behavior with three oscillation modes caused by pulsed X-ray exposure in an SiN X-ray mask membrane has been predicted by simulation using the weighted residual method. The displacement caused by thermal distortion cannot take place during pulsed X-ray exposure with a 10-ns pulse duration in the three dynamic response modes: damped oscillation, critical damping, and overdamping. The damped oscillation mode with an overshooting effect is caused by an elastic wave effect after a 1-µs time lapse. According to the pulse duration effect, the dynamic behavior is divided into three regions: quasi-static, transient, and saturated regions. For the quasi-static region, the elastic wave effect and three oscillation modes can be neglected. Differences in the dynamic behavior occur in the transient region. In the saturated region, the displacement cannot take place during the pulsed X-ray exposure, due to the elastic wave effect.