Modulation transfer function (MTF) value is an important parameter to characterize the imaging performance of mercury cadmium telluride (HgCdTe) infrared detector. Crosstalk is one of the major factors which degrade the MTF value of detector. The reasonable device structure design can effectively suppress crosstalk and improve the MTF value of the device. A HgCdTe infrared focal plane detector with metal frame structure is proposed, which can effectively absorb laterally diffused photo-carriers and suppress crosstalk. We also carry out measurement and analysis of the MTF of the detectors with and without metal frame structure. The experimental results indicate that, compared with the detector without metal frame structure, the detector with metal frame structure can effectively increase MTF value of detector.