It is generally preferred for the non-inverting buck-boost converter to operate in buck mode when the input voltage is higher than the output voltage and in boost mode vice versa to improve the efficiency. However, the performance of the converter would be degraded under this operating scheme when the input voltage approaches to the output voltage due to the occurrence of the dead-zone. The four-mode control method is a potential solution to eliminate the dead-zone issue. This paper is to analyze the operating principle and the performance of the converter with four-mode control method. A prototype with 16.8V output voltage is tested in the laboratory. Analytical and experimental results show that the converter can obtain high efficiency, fast load and input voltage transient response in the entire input voltage range with the four-mode control method.