A foldable clamp-on desk lamp with a multi-angle adjustment function includes: a lamp base part, a clamping base, several supporting rods, and detachable rotating shaft assemblies through which the several supporting rods are movably connected and the lamp base part is connected to the uppermost supporting rod. The lowermost supporting rod is detachably connected to the clamping base. The detachable rotating shaft assemblies can achieve folding and telescopic functions, complete disassembly, repeated disassembly, assembly and change, and long service life. By the design combining a Fresnel lens and convolutional lines, light is continuously scattered and recombined when passing through the convolutional lines, so that the outgoing light is more uniformly, soft, and not dazzling. A plurality of inserting holes are formed at the upper side and top end of the clamping base, thereby facilitating multi-directional assembling of the supporting rods and achieving wide application of the clamping position.