The invention discloses a power battery cover plate and a substrate thereof. A positive pole hole and a negative pole hole through which a positive pole and a negative pole pass are formed in the substrate respectively; square steps are formed on the upper surface of the positive pole hole and the lower surface of the negative pole hole respectively; a circle of nick with an inverted triangular section is further formed on the peripheral upper surface of the negative pole hole. The invention further discloses a power battery cover plate which comprises the substrate. A step embedded into the square step in the positive pole hole in a matching way is formed on the upper surface of the substrate for the positive pole; the positive pole is welded together with the upper surface of the substrate; the positive pole is sleeved with a positive pole protection rubber cushion on the upper surface of the substrate; the negative pole and the negative pole hole are connected with each other in an electrically insulated way through a sealing gasket wrapping the positive pole hole; the sealing gasket is provided with a convex ring embedded into the inverted triangular nick on the upper surface of the substrate. The power battery cover plate and the substrate have the advantages of improving the safety performance of batteries and realizing rapid assembly.