Embodiments and implementations of the present disclosure provide assistant pattern configuration methods, masks and forming methods thereof, and related devices. One form of a configuration method includes: providing a main pattern having an edge extending along a first direction, where a second direction is perpendicular to the first direction, the main pattern having a first optimal focal plane in the first direction and a second optimal focal plane in the second direction when exposed, and where there is an optimal focal plane offset between the first optimal focal plane and the second optimal focal plane; providing an initial assistant pattern around the main pattern; extracting a configuration parameter of the initial assistant pattern, the configuration parameter corresponding to the optimal focal plane offset; obtaining configuration information corresponding to a preset optimal focal plane offset based on an adjustment of the configuration parameter; and configuring an assistant pattern around the main pattern according to the configuration information. Embodiments and implementations of the present disclosure can improve lithographic quality.