Compared with narrowband radars, the high-resolution range profile (HRRP) acquired by wideband radars contain abundant target information that is useful for detection and recognition. However, more and more threatening targets are of low observability and high maneuverability. Therefore, reconstructing HRRPs of maneuvering weak targets from low signal-to-noise ratio (SNR) echoes is a significant but challenging problem. To estimate motion parameters and reconstruct high-SNR HRRP, this paper proposes a long-time coherent integration (LTCI) algorithm based on subband keystone transform (SKT) and extended Lv's distribution (ELVD). In this paper, the range-spread target (RST) assumption is applied in the LTCI processing. Moreover, the proposed SKT-ELVD operations have excellent performance on range migration (RM) correction and integration gain. The proposed algorithm can be of effectiveness in lower SNR conditions, since more energy of target's echo can be accumulated. Theoretical results are initially supported by sufficient simulation examples. Finally, the validity of the proposed algorithm is confirmed by experimental data.