To satisfy the application requirements of laser rangefinders in terrain mapping, shallow coastal detection, and other fields, this study proposes a set of echo reception systems suitable for airborne laser rangefinders. The system measures the absolute distance between the device and sea surface via time-to-digital technology, as well as the relative distance of multiple targets via analog-to-digital converter technology, thus enabling the reception and measurement of echoes from the sea surface and seabed in shallow coastal areas. To address the issue of ranging accuracy affected by errors in the travel time of laser echo signals, this paper proposes an automatic parameter-control algorithm that can automatically adjust the circuit gain and comparator thresholds based on the echo signal. Additionally, the Levenberg-Marquardt (LM) algorithm is used to decompose the echoes, thus effectively improving the accuracy of multitarget echo decomposition. By constructing an experimental system for testing, the results show that the root mean square error of the system for measuring single targets does not exceed 2.89 cm and the accuracy of echo decomposition for dual targets does not exceed 2.56 cm.