In order to clarify the effect of biochar on the physical and chemical properties of the substrate and the efficiency of pepper seedlings, this experiment sets 0, 0.1%, 0.5%, 0.9%, 1.3%, 1.7%, 2.1% biochar application rate（W∶W, %）. Using traditional vermiculite mixed substrate of pastoral soil peat as a contrast, the seedling breeding experiment of greenhouse substrate was carried out. The results show that the addition of biochar can increase the porosity and EC value of the matrix, reduce the water-gas ratio of the matrix, and optimize the selection of the matrix.With the increase of biochar, the growth of pepper seedlings increased at first and then decreased, and all treatments were better than the control. When the biochar supplemental level was 0.9%, the pepper had the best growth, and the shoot dry weight, chlorophyll content and strong seedling index all reached the maximum values（1.53 g, 2.59 g,0.418）, which promoted the seedling growth.