The invention provides a mask, a hole forming method, a display substrate forming method, a display substrate and a display device. The mask is used for forming a hole on a film, and comprises a light-transmittable pattern used for forming the hole; and the light-transmittable pattern has a curved edge. Because the light-transmittable pattern on the mask has the curved edge, the bottom of the hole formed by adoption of the mask also has the curved edge; therefore, the length of a contact boundary line of upper and lower conductive layers electrically connected through the hole can be increased; the contact resistance between the upper and lower conductive layers can be reduced; the connectivity between the upper and lower conductive layers can be improved; in addition, in an exposure process for forming the hole, the transmission amount of light at the edge of the light-transmittable pattern is relatively low; only a part of thickness of the film corresponding to the part can be exposed; therefore, the slope angle of the inner wall of the formed hole is relatively small; the segment gap of the hole can be reduced; breakage of the upper conductive layer in the hole can be avoided; and thus, the connectivity is further improved.