The reasons of this study, to develope a digital tiny fish-finding moudule, are as follows:1. Decreasing limit for wide-band fishfinder signal whatever analog or digital in hundreds mile of distance and hash ocean-condition communication situation.2. Fitting needs for saving oil energy of marine fishing vessels.3. Exploring a module which can be loaded into a small communication host gear and can be used in manless environment. This study is to improve signal processing way of traditional fishfinder and design a tiny fish-finding module with size 54mm diameter and 93mm height. This module contains a target-strength counting device based on a embedded high-level Single-Board-Computer CPU kernel. Separated vertical layers of echo strength of fish schools will be observed and integrated into digital number. This tiny device was designed to be hosted into a small radio/satellite communication buoy and to transmit fish congregation information for determination on operating of fishing vessels.