A series of phosphors Sr0.955Al2－xGaxSi2O8∶Eu2+ (x=0～1.0) was prepared via solid-state reaction in weak reductive atmosphere. Lattice positions and the luminescent mechanism of Eu2+ in the host were discussed, and effects of Ga3+-substitution on the host lattice and spectral properties were investigated. The results showed that complete solid solutions formed in the whole range of x=0～1.0 while Ga3+ entered SrAl2Si2O8 lattice and substituted Al3+. The lattice parameters (a, b, c) and unit cell volume of phosphors Sr0.955Al2－xGaxSi2O8∶Eu2+ (x=0～1.0) increased linearly as Ga3+ content increased in the phosphors. When Ga3+ substituted for Al3+, the most obvious changes happened in cell parameter c, b was the second and a was the minimum. A broad excitation spectrum of Eu2+ presented from 230 nm to 400nm and peaked at 350 nm, which consists of 267 nm, 305 nm, 350 nm and 375 nm excitation bands. The three shorter wavelengths excitation peaks were shifted to red and the peak intensities of 267 nm and 350 nm were decreased. The peak intensity of 305 nm increased significantly while the peak position and intensity of 375 nm unchanged basically as the increased substitution of Ga3+. The FWHM of the apparent excitation peak narrowed from 109 nm to 98 nm. The broad and asymmetric emission spectrum among 380 nm and 600 nm and apparent peak was at 407 nm, which could be fitted by two peaks at 406 nm and 441 nm. The two fitted peaks were red shifted and the intensity ratio of the fitted peaks increased linearly with the increasing of the amount of Ga3+-substitution. The apparent emission peak was red shift from 407 nm to 422 nm and FWHM increased from 58 nm to 79 nm while Ga3+ content was up to 1.0 mol. The distance of Eu-O was shorted due to Al3+ is replaced by Ga3+. The crystal field of the emitting center Eu2+ location was enhanced. The splitting of 5d orbital levels was increased and the lowest emission level was expanded to lower.