The invention relates to a transmission type bauxite on-line neutron activated aluminum silicon ratio analysis device and an analysis method. A measuring device is a gamma detector fixed between an upper belt and a lower belt, a neutron source is placed above the upper belt and the bauxite, neutrons are downwards irradiated on the bauxite on the belt to generate action with nucleus in the bauxite, the gamma detector transforms the received ray into a pulse signal and transmits the pulse signal to a multi-channel energy spectrum analyzer to process, the multi-channel energy spectrum analyzer uploads effective information to an upper computer, and the upper computer calculates the aluminum silicon ratio of the bauxite according to the corresponding formula. The aluminum silicon ratio finally obtained by calculation is a ratio relation between aluminium oxide content and silicon dioxide content, so the aluminum silicon ratio is not influenced by the total amount of the bauxite on the belt; the overall shielding protection of the instrument adopts a two-layer structure, the inner layer is lead and the outer layer is polyethylene, so the use amount of the lead is reduced, and the cost and the weight of the instrument are reduced; and a detector shielding body adopts a two-layer structure, the outer layer is polyethylene and the inner layer is a cadmium plate, so the influence on the gamma detector by the neutrons is minimized, and the analysis precision of the instrument is improved.