Using the velocity operator derived from the Heisenberg equation of motion, we have investigated second‐harmonic generation of acoustic waves propagating in nondegenerate piezoelectric semiconductors with a uniform dc magnetic fieldBdirected along the waves. Since we are interested in both high‐and low‐frequency regions, an electron relaxation time due to the scatterings in solids is taken into account. Results show that the second‐harmonic generation due to the piezoelectric polarization is insignificant in the very low‐frequency region. However, when the frequency is coming into the microwave region, the second‐harmonic generation increases quite rapidly with the sound frequency up to some maximum points at the range of frequency &ohgr;=1011–2×1011rad/s, and then decreases. There are two maximum points in this range of frequency at very low temperatures. When the temperature increases, these two maximum points will be reduced to only a single maximum point. It is also found that the second‐harmonic generation can be influenced by the dc magnetic field due to the nonlinear nature of energy bands in piezoelectric semiconductors.