A grayscale compensating method, an apparatus for a self-luminous display and a self-luminous display device are provided. The method includes: obtaining each driving voltage corresponding to each grayscale signal of the self-luminous display; determining, according to intervals to which each driving voltage belongs, each preset driving function corresponding to each driving voltage; determining each first driving current corresponding to each driving voltage according to each preset driving function; detecting each second driving current of pixel units of the self-luminous display in case of being driven at each driving voltage; comparing the first driving current with the second driving current, and determining compensating voltages corresponding to each grayscale signal according to each preset driving function, and differences between each first driving current and each second driving current.