The invention relates to a method for enhancing anammox granular sludge in UASB, and belongs to the field of urban domestic sewage denitration treatment and recycling. According to the invention, an UASB reactor is adopted. Through improving inlet water flow rate and reflux ratio, through a granular sludge formation stage, a granular sludge enhancing stage, and a granular sludge stabilizing stage, a total nitrogen removal load reaches 6.5kgN/m3/d, and an average particle size is 2.0mm, such that anammox granular sludge is successfully enhanced. The average particle size is larger by 1.27mm compared with the anammox granular sludge cultured by Wang Junmin etc. (2011) with an UASB reactor, and a total nitrogen removal load is higher by 0.77kgN/m3/d.