Since the debut of Dolby in 1992, it now becomes a industrial benchmark of film production and cinema equipment, no matter the public cinema or home theater. Up to 2007, the Dolby Digital technology was applied in 1.65 billion electrical equipment, including 45 millions home theater system . So, let us talk about what is “5.1”; first of all, “5” means there are five surround speakers: front left and right; a center channel and two surround channels. Moreover, the “1” means there is also a subwoofer, because human beings cannot figure out the direction of the low frequency sound sources . Except the Dolby 5.1, it also has some other channel configurations, such as 7.1 and 8; but my report will focus on the 5.1 configuration, because it is the most widely applied and most influential. In that way, how does this technology improve the sound effects such dramatically? For example, if you implement it in a movie, the center channel is responsible for the dialogues of characters and the two speakers, front left and right, are play the sound out of the screen center or even outside the screen. Further more, the two surround speakers are in charge of the background music or peripheral sound and the subwoofer takes the part of low frequency sound, such as the sound of motor or drum.  In short, the 5.1 channel technology makes the viewer to be in the center of the scene, vastly improves the quality of the sound effects and brings the great artistic enjoyment to the audience.