The invention discloses a mask assembly and a manufacturing method of a Mini LED backlight module. After luminous chips are subjected to crystal fixing, the mask assembly is pasted above the luminouschips, all mask regions correspond to the luminous chips one to one, thus, second shielding parts of the mask regions cover the luminous chips, spraying parts correspond to the positions of gaps in the peripheries of the luminous chips, then materials for manufacturing reflecting structures are sprayed to the positions of the gaps of the luminous chips through hollowed-out regions of the sprayingparts to form the reflecting structures, as the materials for manufacturing the reflecting structures can be simultaneously sprayed to the peripheries of the luminous chips, the procedures are simple,the consumed time is short, the spraying efficiency is high, and mass production is achieved; and in the spraying process, the second shielding parts shield the luminous chips, the spraying materialsare prevented from being sprayed onto the luminous chips, and therefore no large welding error is caused to the following Mini LED backlight module.