Abstract: 【Objective】This study aimed to explore the effective of partial substitution of chemical fertilizers with two different bio-organic fertilizers （Roudanbai bio-fertilizer M₁ and Baaiwo bio-fertilizer M₂） in reducing chemical fertilizer application and increasing yield of dryland flax.【Method】With no fertilization as control （CK）,the effects of conventional fertilization （CF）,70%CF+30%bio-organic fertilizer （30%M₁,30%M₂）,40%CF+60%bio-organic fertilizer （60%M₁,60%M₂） and 10%CF+90%bio-organic fertilizer（90%M₁,90%M₂） on the growth characteristics and grain yield of oilseed flax in dryland were studied.【Result】The treatments of replacement partial chemical fertilizer with different bio-organic fertilizers not only significantly increased the maximum and average dry matter accumulation rates of oilseed flax above ground,but also increased the dry matter accumulation amount and the dry matter allocation of reproductive organs at the mature stage of oilseed flax.Among them,the dry matter accumulation under the 30%M₁ treatment was higher by 6.42%～41.74%than those of other treatments.The dry matter distribution of reproductive organs was higher by 0.23%～7.15%than that of other treatments.Otherwise,the bioorganic fertilizer could increase the grain yield by increasing effective capsule number per plant and seed number per fruit.The yield under 30%M₁ and 30%M₂ treatments were significantly increased 25.09%and 23.84%when compared with CF and increased 40.32%and 38.92%when compared with CK,respectively.It indicated that 30%organic fertilizer substitute for chemical fertilizer can promote dry matter accumulation,dry matter distribution of oilseed flax at late growth stage,and increase effective capsule number per plant,seed number per fruit and so as to increase the grain yield of oilseed flax.【Conclusion】The results suggested that the substitution of chemical fertilizers with 30%bio-organic fertilizers could promote the accumulation of dry matter,the distribution of dry matter in flax seeds,the number of effective capsules per plant and the number of seeds per fruit,and thus increase flax yield.Therefore,the fertilizing mode could be a suitable fertilization method of reducing chemical fertilizer and increasing grain yield in oilseed flax cultivation in central area of Gansu.