Array-form ultrahigh sensitivity single-beam atomic magnetometers are ideal for high-resolution biomagnetic imaging applications, such as magnetocardiography and magnetoence-phalography. In the low-frequency range of interest for biomagnetism, an essential reason for the deterioration of atomic magnetometer low-frequency sensitivity is the light shift noise caused by temperature fluctuations of the pump laser. Accordingly, this article proposes a new frequency response model of the atomic magnetometer sensitivity, treating light shift as a time-dependent variable. The model reveals the frequency relationship between the deterioration of atomic magnetometer sensitivity and the low-frequency light shift. A new method for suppressing the low-frequency light shift noise based on precise laser temperature control is deduced from the frequency response model, significantly improving the average sensitivity of atomic magnetometers by over 30%. This study presents a theoretical foundation for investigating the low-frequency light shift in atomic magnetometers from a novel perspective and contributes to the optimization of biomagnetic imaging systems composed of single-beam atomic magnetometers.