To promote the technical progress and popularization of ecological protection of swelling soil slopes, the characteristic that poor swelling soil is unfavorable to vegetation growth was considered, and a method of improving soil quality by using organic fertilizer was proposed, so as to better play the role of vetiver in protection of swelling soil slopes. The swelling soil from Guangxi Province was used as the research object, and compaction and swelling rate tests on swelling soil with different fertilizer contents were conducted to study the effect of organic fertilizer addition on the characteristics of swelling soil. Meanwhile, the partial factorial experimental design was used to study the effect of different organic fertilizer, slow-release fertilizer, and straw contents on the root system growth of vetiver and swelling of the root-soil complex. The results show that the maximum dry density of swelling soil decreases with the increase in organic fertilizer content, and the optimum moisture content and unloaded swelling rate increase with the increase in organic fertilizer content. The effect of slow-release fertilizer in promoting the early fertilization of vetiver is significant; straw can inhibit swelling, but it does not affect recent root system development. The improvement of root number and swelling rate is the most obvious when the organic fertilizer content is 5%, and the promotion effect of organic fertilizer on root system growth can compensate for its adverse effect on swelling soil. With the increase in organic fertilizer content, the improvement effect of root growth and swelling rate slows down.