Abstract: To investigate the filtration mechanism of acidizing fluid in the fractured reservoirs in Tahe and increase the fluid efficiency in the process of acid fracturing, four key factors of acidizing fluid filtration (i.e., acidizing fluid type, alternative injection stage, prepad fluid proportion and acid injection displacement) were evaluated based on fracture network model by using the independently developed visual filtration simulation and evaluation unit of acid etched fracture.It is indicated that the effect is apparent at the inlet end of gelling acid, the fracture width at the inlet end is much larger than that at the distal end, the width of fractures etched by surface crosslinked acid is uniform and the erosion effect in deep part is good.Besides, the acidizing fluid filtration decreases with the increase of alternative injection stages, and the optimal stage number of multistage alternative injection acid fracturing in Tahe is 3-5.The etched width and depth of distal fractures increase with the increase of prepad fluid proportion.In Well YJX, 3-stage alternative injection acid fracturing technology is adopted and the acid injection displacement is increased to 7 m³/min.Its acid fracturing fluid efficiency and acid etched fracture length are much greater than its neighboring well, acidizing fluid filtration is decreased significantly and the stimulation effect is remarkable with postfrac cumulative oil production of 1.5×10⁴ t.