The utility model relates to a precise plastic helical gear mould. The preciseplastic helical gear mould comprises a fixed mould and a movable mould, and is characterized in that the fixed mould comprises an installation plate, a stripper plate, a fixed mould plate and an embedded piece of a fixed mould chamber, and the movable mould comprises a movable mould base plate fixed by bolts, square iron, a substrate, a movable mould plate and an embedded piece of a movablemould chamber, wherein the