The quantum properties of weak cohetent state in terms of squeezing effect and antibunching effect were investigated in the diffusion. Master equation of density operator in the diffusion process can be concisely solved by virtue of thermo-entangled state representation and the technique of integration within an ordered product of operators, which contains normal ordering, antinormal ordering and Weyl ordering. The solution of master equation of density operator in diffusion process was given by Kraus operator. The evolution formula of the field density operator which is in weak coherent state initially was get . Its squeezing effect and antibunching are investigated by the numerical method. The effect of decoherence on its nonclassical property is discussed. Numerical results show that compression depth is weakened and the compression range decreases with diffusion time increasing. On the other hand, the light field displays antibunching effect in the early diffusion. When the diffusion time is greater than a certain value, its antibunching effect disappears.