The photosynthetic characteristics of Echium vulgare under different N, P and K fertilizer treatments were measured and analyzed by using Li-6400 type photosynthetic apparatus to understand the regularity of diurnal variation of photosynthetic characteristics of Echium vulgare. The result showed that photosynthetic diurnal variation curve of Echium vulgare changed under different N, P and K treatments. N and P were single peak curve, but K was a bimodal curve. The maximum photosynthetic rate of the three fertilizer treatments was K, and its maximum of bimodal curve of the net photosynthetic rate was 22.364 μmol（CO₂）/（m²·s） at 10:00 am. The correlation between photosynthetic rate and photosynthetic parameters showed no significant difference. However, there was a significant correlation between photosynthetic parameters. It showed that the diurnal variation of photosynthetic rate was affected by the combined factors of the photosynthetic characteristic parameters. K results in diurnal variation of photosynthetic rate in bimodal curve was affected by inter cellular CO₂ concentration（Ci）. By variance analysis, the variance of K variance was smallest（4.14） and the minimum was 2.51. N and P did not appear midday depression of photosynthesis, and could provide theoretical support for high-yield cultivation techniques of Echium vulgare.