The invention relates to the technical field of digital signal processing, and discloses an ultralow-sidelobe pulse compression method. The method specifically comprises the following steps: S1, a transmitter designs a weighted window function w(t) according to a transmitted linear frequency modulation signal s (t), and converts the transmitted signal into s(t)*w(t); S2, a corresponding pulse compression matched filter h(t) and a corresponding sidelobe suppression filter w(t) are designed at a receiver according to the transmitted signal, wherein the sidelobe suppression filter w(t) is designed according to the weighted window function w(t); S3, the pulse compression result y(t)=[s(t)*w(t)]*[h(t)*w(t)] of an echo signal is calculated according to the matched filter h(t) and the sidelobe suppression filter w(t) at the receiver; S4, the weighted window function at the transmitter is cancelled, an equivalent filter hw(t) is designed at the receiver, and an equivalent filter hw(n) is calculated according to a frequency domain implementation method; and S5, the transmitter transmits the linear frequency modulation signal s(t), the receiver designs a pulse compression equivalent filter hw(n), and ultralow sidelobe is obtained. By adding window functions at the transmitter and the receiver respectively, sidelobe is reduced effectively.