We study the two-dimensional weak-coupling Fr(o)hlich polaron in a completely anisotropic quantum dot in a perpendicular magnetic field.By performing a unitary transformation,we first transform the Hamiltonian into a new one which describes an anisotropic harmonic oscillator with new mass and trapping frequencies interacting with the same phonon bath but with different interaction form and strength.Then employing the second-order Rayleigh-Schr(o)dinger perturbation theory,we obtain the polaron correction to the ground-state energy.The magnetic field and anisotropic effects on the polaron correction to the ground-state energy are discussed.