The invention discloses a water phase preparation method of a spherical 
silver nanoparticle with adjustable size, which comprises the following steps of: 10, preparing a silver seed solution : 101, mixing deionized water with a 
sodium citrate solution, and obtaining a stabilizer solution after stirring; 102, heating the stabilizer solution to the temperature of water bath, adding an AgNO3 solution, and then adding a NaHB4 solution; and 103, utilizing the deionized water to obtain a constant volume after cooling at 
room temperature, and obtaining the silver seed solution; 20, preparing the spherical 
silver nanoparticle: 201, adding deionized water to a flask, then adding 
sodium citrate solution to obtain a 
reducer solution, and heating the 
reducer solution to a boiling state; 202, adding the silver seed solution to the 
reducer solution, and then adding the AgNO3 solution; and 203, cooling at 
room temperature to obtain the spherical 
silver nanoparticle. The preparation method can be used for preparing the spherical silver 
nanoparticle with favorable monodispersity, and the size of the spherical silver 
nanoparticle can be adjusted.