[Objective] A field experiment was conducted in paddy fields in the Dianshan Lake region of Shanghai to explore effects of raising ducks in paddy fields on soil nutrients, field surface water, rice growth, and control of weeds, pests and diseases.[Method] The experiment was designed to have three treatments and one CK, i.e. duck-raising in paddy field (DR); No duck-raising in the fields irrigated with drainage from Treatment DR(ND); No duck-raising in the field irrigated with drainage from Treatment DR, plus manual weeding (NDW); and rice cultivated as usual with irrigation of normal water (CK). No pesticides and herbicides were applied during the whole experiment to prevent their disturbances to rice and duck growth, soil nutrients and enzyme activities.[Result] Results show that all of the treatments, no matter whether it was directly affected by duck raising (Treatment DR), or indirectly affected by irrigation (Treatments NDW and ND), increased the content of soil nutrients. Treatment DR was the highest in the effect, being 11.0%, 17.6%, 11.5%, 13.3% and 13.6% higher in content of total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, readily available potassium and organic matter in the soil, respectively, than CK during the rice growth season, and Treatment NDW and ND was 9.8%, 8.4% and 10.9% higher, and 3.4%, 2.1%, and 7.1% higher than CK, respectively, in content of alkali-hydrolyzable nitrogen, available phosphorus, and readily available potassium. Meanwhile, stirring of the flooding water by ducks in Treatment DR increased the content of dissolved oxygen and hence microbial biomass and activities of soil enzymes, especially the activity of urease, catalase and sucrase, by 21.0%, 20.6% and 13.9%, respectively. Thanks to the activities and fecal excretion of ducks in Treatment DR, the flooding water in Treatments DR, ND and NDW was significantly higher than that in CK (P<0.05) in nutrient content. Especially on September 26, the flooding water in Treatment DR peaked up to 1.18 mg·L^-1, 0.40 mg·L^-1 and 0.93 mg·L^-1, respectively in contents of ammonium nitrogen and available and total phosphorus, or was 137%, 177% and 316% higher than in CK. Pecking, trampling and stirring of the ducks in the fields effectively inhibited weed growth, reducing the density of weeds by 91.6% on average in Treatment DR. In contrast, the density of weeds was the highest in Treatment ND and then in Treatment NDW and in Treatment DR, suggesting that the effects of regular manual weeding in the paddy fields on weed control were not so good as that of raising ducks in paddy fields. All the treatments, DR, NDW and ND, stimulated tillering of the rice significantly or by 34.2%, 32.1% and 33.6%, respectively. The incidence of rice leaf rollers, sheath blight or rice planthoppers was significantly lower in Treatment DR than in CK and the other treatments. Moreover, Treatment DR was also significant in yield increasing effect, with grain yield reaching up to 8 507 kg·hm^-2, 1.42 times that of CK. [Conclusions] In general, raising ducks in paddy fields can improve soil fertility, inhibit weeds and reduce incidence of rice pests and diseases effectively, which is beneficial to minimizing the utilization of pesticides, herbicides and chemical fertilizers in paddy fields and controlling non-point source agricultural pollution. Moreover, it helps produce high quality healthy food-rice and ducks.