The invention discloses a method for measuring a gas and water production dynamic relative permeability curve in undersaturation coal reservoir development. The method comprises the steps that gas well accumulation production Q is obtained; a production phase of a production well is judged; reservoir pressure p and reservoir water saturation Sw are obtained; the reservoir pressure p is introduced into an improved absolute permeability model, and the absolute permeability K is obtained; irreducible water saturation Swr is predicted by measuring the porosity phi; the reservoir water saturation Sw and the irreducible water saturation Swr are introduced into a relative permeability model, and the relative permeability kr is obtained; the relative permeability and the absolute permeability are coupled on the condition of the identical the reservoir pressure p and the identical reservoir water saturation Sw, and the effective permeability ke at the moment is obtained. The method solves the problem of measuring the undersaturation coal reservoir gas and water relative permeability curve, the positive and negative effects and the slippage effect in the developing process are taken into consideration, the changes of a two-phase common flow area relative permeability curve can be represented, the changes of a single-phase water stage relative permeability curve can be better represented, the influence of water invasion is taken into consideration, and the actual production of undersaturation coal gas reservoirs are better met; a nuclear magnetic resonance method is used, convenience, fastness and non-destruction are achieved, precision is higher, and practicability is higher.