The acoustic stealth shape design of the underwater vehicle becomes a topic of considerable current interest to the experts engaging underwater acoustic countermeasure technology in recent years. During tracking the target, the echo strength (ES) of head shape is easily exposed and detected for the underwater vehicle, which directly affects its acoustic stealth performance. This paper proposes an optimal design method for the acoustic stealth shape of the underwater vehicle head with relatively lower target strength (TS), based on the Nelder-Mead optimization algorithm and Finite Element Method (FEM). In this method, Bernstein polynomials are used to describe the underwater vehicle head shape deviation, and the optimization objective function is given as the weighting function of the TS of underwater vehicles head with different angles and frequencies. Then the two optimized results with different situations are given, which the angle detecting rate is used to evaluate. Finally, the 2D axisymmetric calculation method of the underwater acoustic scattering field is used to verify the TS calculation in this paper. The optimization design method may provide guidance for the lower TS shape design of the underwater vehicle, which may realize the automatic design of the lower TS shape with incident plane waves at given angles and given frequencybands.