Abstract: The effects of four spray adjuvants(AY904-1,containing 40% P(VAc-co-AA ) and 10% isomeric alcohol ethoxylates; AY904-2, containing 30% P(VAc-co-MA) and 10% isomeric alcohol ethoxylates; AY904-3, containing 20% P(VAc-co-EA) and 10% isomeric alcohol ethoxylates; AY904-4, containing 10% P(VAc-co-BA) and 10% isomeric alcohol ethoxylates) on rainfastness of azoxystrobin on the leaf surfaces of maize were studied under lab-washing conditions. Fluorescence microscopy and HPLC were used to detect the change of fluorescence coverage and the content of azoxystrobin dry deposits on the leaves of maize before and after washing. Besides the physical characteristics of tank-mixed solution and the swelling of solution cast adjuvant films in different temperature were studied. The safety issues of spray adjuvants mixed with 200 g/L chlorantranilone SC 3 000 times to maize was also studied under greenhouse conditions. The results showed that the addition of the above mentioned four spray adjuvants could increase the retention of azoxystrobin on maize leaves in different levels, and the results obtained using Fluorescence microscopy and HPLC had a good correlation. The treatments of AY904-1 and AY904-2 at mass fraction from 0.1% to 1.0% and the treatments of AY904-3 and AY904-4 at mass fraction from 0.5% to 1.0% significantly improved the retention of the azoxystrobin on the maize leaves. Higher concentration of adjuvants resulted in better resistance to erosion. Among all the adjuvants, AY904-1 afforded the best performance. Compared with blank control, all those spray adjuvants could shorten the liquid drying time and reduce the contact angle on the corn leaf surface. However, there was no significant difference compared with the azoxystrobin control. The films of AY904-1 and AY904-2 have lower degree of swelling in water and better film-forming properties. In addition, all of the adjuvants are safe to three varieties of maize.