Abstract: The infrared waveband can detect enough stars for navigation. The contrast of star to sky background is an important parameter of star detection during daytime. This paper analyzed the 6 magnitude star contrast changing with the solar zenith angle, detector height and detection azimuth in near-infrared band. Results show that the star to sky background contrast performs approximate exponential growth with the solar zenith angle, and the contrast with 40solar zenith angle is about 2.69 times of 20;above a certain height, the contrast performs approximate exponential growth with the increase of detector height, it is lower than 3 when the height is less than 15km, but increasing quickly to 60 at 80km; the star to sky background contrast nearly increases linearly with the increase of detection azimuth, and the contrast with 30azimuth is 2.38 times of 0.