The invention relates to a substrate salt content automatically adjusting soilless vegetable planting method. The method comprises collecting substrate water content data at a fixed time interval; determining whether substrate water content is lower than a water stress critical value, if so, performing irrigation through nutrient solution; estimating substrate salt content; determining whether the substrate salt content is higher than a salt damage critical value, if so, performing rinsing through the nutrient solution; repeating the above steps until the growing period ends. Meanwhile, the invention provides a substrate salt content automatically adjusting soilless vegetable planting system applying the method. The substrate salt content automatically adjusting soilless vegetable planting method and system achieves automatic adjustment of soilless planting substrate salt content, saves human resource costs and fund costs, ensures fine water and fertilizer supply of soilless planted crops, avoids salt damage to the crops, and meanwhile, reduces waste of the nutrient solution, maximizes the utilization rate of the nutrient solution and provides technical guarantee for high-quality and high-efficiency yield of the soilless planted crops.