A dual-band negative group delay (NGD) microwave circuit with low signal-attenuation and arbitrary frequency ratio is proposed. Closed-form analytical equations are derived for the design of the proposed dual-band negative group delay circuit (NGDC) with the variable frequency ratio. The characteristic parameters of the microstrip lines that influence the frequency ratio are investigated. Under the condition that the microstrip circuit can be implemented with the common printed circuit board (PCB) fabrication technology, the frequency ratio can vary between 1.1 and 6.3. For verification, three dual-band NGDCs with the frequency ratio of 1.105, 3, and 5.667 are designed, fabricated, and measured. Good agreements are observed between simulated and measured results, indicating the validity of the proposed methods.