When magnetic signals are measured by triaxial magnetic flux gate sensors,its axes should be known beforehand.However,some difficulties are met in fixing the axes of sensors,so the axes of sensors can't be known in advance.These cause some trouble in magnetic field measurement.Focusing on this problem,a formula is given,from which orientations of the axes of triaxial magnetic flux gate sensors can be achieved.Also,an error formula is deduced when considering background magnetic noises.Then a simulation experiment and an actual experiment are designed to analyze the influences on orientations of the axes of triaxial magnetic flux gate sensors caused by background magnetic noises.The results show that background magnetic noises should be strictly controlled to reduce errors in the magnetic field measurement with high accuracy.Therefore this is instructive in the magnetic field measurement.