Disclosed is a pulse laser signal-to-noise ratio detection device, which includes a first fiber optic splitter, a delay fiber, an adjustable delayer, a polarization controller, a pulse bias generator,a dual-stage electrooptic intensity modulator, a second fiber optic splitter, a trigger unit, an attenuation device, a delay device, a signal gain device, a multi-optical path multiplexing device, aphotoelectric detection device, an electric signal processing device and the like. The pulse laser signal-to-noise ratio detection device in the invention detects the background noise intensity of thelaser output pulse by using the first fiber optic splitter, the delay fiber, the adjustable delayer, the polarization controller, the pulse bias generator, the dual-stage intensity modulator, the second fiber optic splitter, the trigger unit and the signal gain device, detects the signal intensity of the main peak of the pulse at the same time by using the first fiber optic splitter, the second fiber optic splitter, the attenuation device and the delay device, and obtains the signal-to-noise ratio. The detection range of the signal-to-noise ratio of the device can reach 50dB with an accuracyof 1dB. The device has the characteristics of easy operation, high test accuracy, good reliability and the like.