The invention provides a jet flow supporting and testing device for turning long and thin rods. The jet flow supporting and testing device comprises a jet device, a cutting force measuring device, a fixture device and the like. The jet device is formed by a handcart, a motor, a high-pressure pump, a water inlet pipe, a water outlet pipe, a spray gun, and the like. The cutting force measuring device is mainly formed by a universal dynamometer, an amplifier, a computer and the like. The fixture device is formed by a clamping piece, a clamping block, a rod piece, a connecting block, a supporting plate, a base plate and the like. The jet flow supporting and testing device can be used for carrying out jet flow basic experiments, carrying out jet-flow or non-jet-flow supporting contrast experiments on turning of the long and thin rods, studying the probability and practical application effects that jet flow is used as auxiliary supporting for turning of the long and thin rods.