Objective To analyze the pattern of visual field （VF） defects and evaluate the correlation between tumor volume and visual function in patients with pituitary tumors. Methods A retrospective analysis of the pre-operative medical history and visual field reports of 42 cases of pituitary tumor was done between January 2013 and August 2014. Mean deviation （MD）， pattern standard deviation （PSD） and visual field index （VFI） of the VF parameter were used to measure VF defect severity， to analyze the pattern of VF defects， and to correlate tumor volume and VF defects. Results Twenty-five patients （60%） complained of reduced vision. Thirty-four patients （81%） showed abnormal VF and 15 of them had bitemporal field changes， which were the most common field defects on presentation. Tumor volume showed a significant correlation with MD and the VFI of the worst eye（MD： r=-0.548， P<0.01； VFI： r=-0.544， P<0.01）. The MD， PSD， VFI， integrated VFI and tumor volume were significantly different in the H-P-A groups （MD： F=24.517， P<0.01； PSD： F=3.452， P<0.05； VFI： F=27.431， P<0.01； integrated VFI： F=21.057， P<0.01； tumor volume F=2.985， P<0.05）. Conclusion The damage to visual acuity and visual field are the main manifestations in patients with pituitary tumors． The larger the tumor， the more severe the damage of VF and visual function.