The invention discloses a self-priming adapter of a vehicle washing solution. The self-priming adapter of the vehicle washing solution comprises a hollow adapter body, wherein the body integrally consists of a water inlet section communicated with a water inlet pipe by one end, a liquid outlet section communicated with a liquid spraying pipe by the other end, and a line cavity section in the middle; the apertures of the water inlet section and the liquid outlet section are larger than the aperture of the line cavity section; a runner of the line cavity section consists of a truncated cone hole and a round hole; the starting end of the truncated cone hole is communicated with the water inlet section; the aperture of the starting end of the truncated cone hole is larger than the aperture of the tail end of the truncated cone hole; the aperture of the tail end of the truncated cone hole is smaller than the aperture of the round hole; a liquid inlet communicated with the washing solution is formed in the side surface of the line cavity section corresponding to the position of the round hole; a ball valve is sealed and mounted in the liquid inlet; and the washing solution is communicated with the liquid inlet through the ball valve. The self-priming adapter of the vehicle washing solution saves electricity and water, and is environment-friendly and low in cost; and one adapter is only needed to replace matched mechanical equipment required in the traditional vehicle washing solution spraying link, so that the operation use cost is largely reduced.