The invention provides a transmission-type prepositive optical path structure used for an ICP spectrometer and having a two-dimensional adjustable function, belonging to the technical field of beam splitting systems for the ICP spectrometer. The transmission-type prepositive optical path structure comprises a front optical barrel, a lens fixing base, a sealing ring, an adjusting base, a thread sleeve, a screw, a back lens barrel, an adjusting ring, a spring, a lifting pin, a lock nut, a slip ring, a lens basic ring and a lens pressing ring. Through two-dimensional adjusting of a prepositive lens, changes of the value of detected signals received by a detector are monitored in real time; and when the signal of the detector reaches a maximum extent, it may be considered that the central hole of the lens and the center of an incident pin hole are of same height and are coaxial, and luminous flux of an echelle grating spectrometer is maximized at the time, so optimal analysis capability of the ICP spectrometer is guaranteed. Meanwhile, as six air vent holes are arranged in the adjusting ring, air in an optical chamber is discharged while argon is introduced into a beam splitting system, so absorption of ultraviolet bands by air is restricted, detection limits of ultraviolet bands are lowered, and the application scope of the ICP spectrometer is further broadened.