The invention relates to an efficiency calculation method for a novel SCR (Selective Catalytic Reduction) denitration device. The efficiency calculation method comprises the following steps: (1) selecting and sampling a sampling measuring point in the manner as specified in GB/T16157-1996 Method for Determining Particulate Matters in Stationary Pollution Source Exhaust Gas and Sampling Gaseous Pollutants 4.2; and (2) performing sampling measurement for flue gas flow speed, oxygen concentration and nitric oxide concentration at each sampling point at the inlet and outlet of the SCR denitration device, adding the flue gas flow speed and calculating nitric oxide concentration and efficiency in the flue gas. According to the efficiency calculation method, the flue gas flow speed is added as the factor participating into the calculation in a detection process, the calculated nitric oxide concentration is more accurate and scientific, and the calculated denitration efficiency more conforms to the practical operation condition of the equipment.