The invention discloses a composite liquid, a treatment liquid and a method for controlling saprolegniasis during an incubation period of freshwater fish viscid eggs. The composite liquid is preparedfrom the components of clotrimazole, diatomite, anhydrous sodium sulfate, ferrous sulfate, gallnut seed, and an antitackiness agent; the treatment liquid is prepared from the components of a complex liquid, magnesium silicate and sodium chloride. The method comprises the following steps: soaking an incubating tool into the complex solution, then pouring freshwater fish fertilized ova into the treatment liquid until the freshwater fish fertilized ova into a dispersed granular shape, then carrying out flow water incubation, and adding the composite liquid during the incubation period. Compared with the prior art, according to the composite liquid, the treatment liquid and the method for controlling saprolegniasis during an incubation period of freshwater fish viscid eggs, through selection of hatchery water source, hatchery tools, and a series of preliminary disinfection and impurity removal measures, the special composite liquid is used cooperatively in flow water incubation, and an accurate hatching parameter is controlled, during an entire incubation process, effective suppression of saprolegniasis during an incubation period of freshwater fish viscid eggs is achieved, occurrenceand spread of the saprolegniasis are fundamentally solved, and breeding rate of freshwater fish is increased.