Electromagnetic metasurface, as a type of planar electromagnetic material consisting of single-layer or multilayer subwavelength artificial micro-structure, can efficiently control the polarization, amplitude and phase of electromagnetic wave on a subwavelength scale. However, confining electromagnetic waves to a deep-subwavelength scale generally is at the cost of a large loss, such as radiation loss, Ohmic loss. Interestingly, non-Hermitian physics provides us a new way to transform the disadvantage of loss into a new degree of freedom in metasurface design, paving the way to expanding the functionalities of metasurfaces. In recent years, the extraordinary effects in the non-Hermitian electromagnetic metasurfaces have attracted a lot of attention. In this review, we discuss the perfect absorption, exceptional points and surfaces waves of non-Hermitian electromagnetic metasurfaces, and point out the challenges and potentials in this field.