To identify suitable plant growth regulators in flax production, enhance lodging resistance and increase yield, different levels of paclobutrazol [975 (D1), 1125 (D2), 1275 g/ha (D3)], uniconazole [750 (X1), 900 (X2), 1050 g/ha (X3)] and chlormequat [1200 (A1), 1800 (A2), 2400 mL/ha (A3)] were applied. The changes of plant growth and development, lodging resistance, seed yield and related traits of flax at different levels were studied with clear water as control (CK). The results showed that spraying three plant growth regulators affected the main agronomic traits of flax. Compared with CK, the number of effective branches of D1 treatment decreased, and the number of effective branches and the number of effective capsules per plant of A1 treatment were lower than those of CK. There was no significant difference in root length among the treatments. The root diameter of A2 treatment was significantly higher than that of CK, and the number of seeds per capsule of each treatment was lower than that of CK. The yield per plant of X2 and A2 treatments was significantly higher than that of CK, and the 1000-grain weight of D1 treatment was significantly lower than that of CK. The plant height and center of gravity height of X3 treatment decreased the most, which were 13.63% and 10.34%, respectively. The stem diameter of each treatment was increased compared with CK, and the D2 treatment increased the most, which was 17.5%. There was no significant difference in yield between any treatment and CK. The stem breaking resistance of A2 treatment was significantly higher than that of CK, and there was no significant difference between the other treatments and the control. The lodging index of each treatment was lower than that of CK, except for D1 and D2 treatments, the other treatments were significantly different.The correlation analysis showed that the effective number of capsules per plant, effective branch number, breaking resistance and root diameter were significantly correlated with the yield per plant, and the fresh weight and crown weight were significantly correlated with the lodging index. Through comprehensive analysis, uniconazole was better than chlormequat, chlormequat was better than paclobutrazol, and uniconazole 900 g/ha had better effect in flax production.