The invention discloses a single-body universal proportional valve and a spraying tank. The single-body universal proportional valve comprises a valve bonnet. An inner cavity is formed inside the valve bonnet. A liquid inlet communicated with the inner cavity is formed in the lower end of the valve bonnet. A proportional valve mechanism is arranged inside the inner cavity in the upper end of the valve bonnet. A universal valve element mechanism capable of achieving liquid inflow when used in an inverted manner is arranged inside the portion, between the proportional valve mechanism and the liquid inlet, of the valve bonnet. The single-body universal proportional valve aims at overcoming the defects in the prior art, is simple in structure, convenient to use, safe, reliable and capable of achieving quantitative liquid spraying and is not limited by the using direction.