In this study, using the extended Huygens-Fresnel principle and the improved Rytov method, a turbulence channel model based on the Gamma-Gamma intensity probability distribution is used to obtain the analytical expression of outage probability. On this basis, the outage probability characteristics of the heterodyne differential phase-shift keying (DPSK) modulation of Gaussian beam waves are studied in anisotropic turbulence. A performance study under different anisotropic ocean turbulence conditions is conducted. The effects of various turbulence parameters, i.e., the contributions of temperature and salinity to the power spectrum, the dissipation rate of kinetic energy per unit mass fluid, and the dissipation rate of mean-squared temperature, are investigated, and the transmission distance and data transmission rate on outage probability are analyzed. The analysis provides a theoretical basis for reducing the outage probability of Gaussian beam DPSK modulation and improving communication quality and reliability.