The invention provides a front-injection back-extraction parallel coal seam inclined drilling gas control device and method. The device comprises double hole sealing pipes, an air bag, a plastic pipeline, a sponge body, a clamp hoop, an inflating device, a grouting pipe, a fixed retainer ring and a sliding device; one hole reaches dual purposes; the front end is used for gas displacement through water injection, and the back end is used for gas extraction through negative pressure; through a blade-shaped iron sheet arranged on the inner wall of an inner pipe and a front-dense and back-sparse sponge body which is arranged at the front half part of a pressure relieving region and can be expended after meeting water, the problem of water injection nonuniformity due to broken degree of the loose coal body of the front half part of the pressure relieving region is solved; and excessive water solution can be prevented from flowing out from big pores of loose coal bodies. By using the front-injection back-extraction method, the air leakage from the pores and cracks of the loose coal bodies can be prevented; the coal seam gas extraction efficiency is improved; free gas of the loose coal body can be effectively expelled; the desorption of adsorption gas can be inhibited; and the gas gushing quantity during the working face stoping is reduced.