Symmetrical slit-step Fourier numerical method is used to simulate the soliton transmission properties in the fibers presenting birefringence. The inferences of the group velocity mismatch (GVM), which denotes the magnitude of the birefringence, on the soliton transmission are analyzed. It is shown that the intensity of the two polarization component of the soliton are hardly varying when the GVM is small, and the soliton is undeformed on the whole in the transmission process. When the GVM is greater, the wider the width and the weaker the intensity of the soliton pulse become rapidly, and the soliton can not undeform transmission. If the birefringence of the fiber is randomly varying, the intensity of the two polarization component of the soliton is changed irregularly with the transmission distance, and the composite intensity of the soliton pulse is hardly varied as the two polarization component compensates each other. The interaction of solitons is influenced by the magnitude of the birefringence; the greater the GVM is, the shorter distance of the soliton with no-interaction. If amplitude rate is chosen appropriately, using the traditional unequal amplitude imputing method, it can still restrain the interaction of the solitons effectively.