The invention provides a two-way unidirectional resistance changing method of a valve. The method comprises the steps that firstly, when fluid flows down, the fluid flows towards a middle pipeline from a first pipeline, at this moment, the pressure of the fluid automatically switches a blocking mechanism to a full open state from a closed state, and the fluid passes through the middle pipeline toflow into a second pipeline; then, after down flowing is finished, the blocking mechanism is switched to the closed state from the full open state; then, when the fluid flows reversely, the pressure of the reversely-flowing fluid enables blocking plates to be close, the blocking mechanism is in the closed state, and the fluid is prevented from returning; and in the third step, when reverse communication is needed, an adjusting mechanism enables the blocking mechanism to overcome elastic force of a pressing spring and the pressure of the reversely-flowing fluid to be switched to a semi-open state from the closed state, the size of an opening of the end, close to a second guide pipe, of the blocking mechanism can be manually adjusted, the resistance of the blocking mechanism to reverse flowing of the fluid is changed, and the process of reverse flowing of the fluid is delayed.