In this paper the amplitude-squared squeezing in the multiphoton nonlinear optical processes is studied. It is examined that amplitude-squared squeezing can be created in the first order approximation by k-photon unitary operators Sk(z) (K>2) acting on the coherent state |α>(|α|≠0) and one can not be created by Sk(z) (K>2, K≠4) acting on the vacuum state. It is found that amplitude-squared squeezing can be created by 4-photon unitary operator S4(z) acting on the vacuum state and this shows that the amplitude-squared squeezing can be created by 4-photon unitary operator S4(z) acting on the vacuum state and this shows that the amplitude-squared squeezing is a new nonclassical effect of light field which is independent of the second order squeezing, antibunching and sub-poisson statistics.