The invention provides a technical method of gas extraction in a mining fractured zone based on kilometer directional drilling. On the basis of analysis of fracture development of overlying strata on a coal face and the gas delivery law, the layer position, length, number, spacing, extraction negative pressure, extraction time and other technical parameters of kilometer directional drilling are determined, several kilometer directional drilling holes are formed in a fissure zone on the upper portion of a goaf in a drill site on the return air side by using a kilometer directional drilling machine, and extraction of gas in the mining fissure zone is conducted until the back production of the coal face is completed. The method is good in extraction effect, low in construction cost, short in engineering cycle and high in work efficiency and can effectively solve the problems that gas is accumulated and overruns at the upper corner and in the goaf.