Based on niche-fitness model, the suitability to habitat conditions of crops under four patterns was evaluated in order to reveal the optimal intercropping pattern of lettuce. And the four patterns were intercropping of lettuce with Chinese cabbage, radish, pea seedling and coriander, respectively. The niche-fitness values of intercropping patterns of lettuce with Chinese cabbage, radish and pea seedling were higher and closer, which showed that the habitat conditions of the three patterns can meet the needs of crops and the habitat conditions were more suitable for their growth. Then TOPSIS model was used to optimize the evaluation results. The relative approaching degrees of the three intercropping patterns with the ideal scheme were 0.557, 0.800 and 0.265, respectively. It was showed that the intercropping pattern of lettuce with radish was relatively close to the ideal scheme, which meant that the intercropping pattern of lettuce with radish was the best pattern among the four intercropping patterns. Considering the actual physiological indexes, it can be drawn that the intercropping pattern of lettuce with radish not only had better effect on the growth of aerosol cultured lettuce, but also had better effect on reducing the nitrate content in lettuce leaves. The combination of niche-fitness model and TOPSIS model had a certain practical significance and it can be used for the optimal selection of different intercropping patterns of lettuce. Limiting factor model was used to analyze, and the results showed that the limiting factor of the intercropping pattern of lettuce with radish was the content of potassium in nutrient solution. The results provided reference for the quantitative analysis of optimization of intercropping patterns.