The invention discloses a capillary tube injection interface device for a nanoparticle aerosol mass spectrometer. The device comprising a general-purpose connector, a buffer chamber, a capillary tube, a focusing lens and a differential chamber, wherein the general-purpose connector, the buffer chamber, the capillary tube, the focusing lens and the differential chamber are successively connected. The general-purpose connector is provided with an aerosol inlet and a current-limiting hole, wherein the aerosol inlet and the current-limiting hole are connected with an aerosol particle pretreatment instrument. The capillary tube which is connected with the buffer chamber, positioning ceramic, a positioning screw, the focusing lens on the rear side of the capillary tube, an insulation straight cylinder which fixes the focusing lens and the positioning ceramic, and a differential chamber outlet in the rear end of the focusing lens are arranged in the differential chamber. The positioning ceramic and the positioning screw are used for fixing the capillary tube. Voltage is applied on the surface of the capillary tube. The influence of Brownian motion in nanoparticle transport is compensated through the action of an electric field, so that charged nanoparticles can converge on the axis of the capillary tube. The gas accompanying matters of the charged nanoparticles can be removed by a vacuum pump which is connected with the differential chamber. The focusing lens can further converge the charged nanoparticles. Atmospheric pressure sample injection and high efficiency transmission of the nanoparticles are realized.