  Let $B(H)$ be the algebra of all bounded operators on a Hilbert space $H$.
Let $T=V|T|$ be the polar decomposition of an operator $T\in B(H)$. The mean
transform of $T$ is defined by $M(T)=\frac{T+|T|V}{2}$. In this paper, we
discuss several properties related to the spectrum, the kernel, the image, the
polar decomposition of mean transform. Moreover, we investigate the image and
preimage by the mean transform of some class of operators as positive, normal,
unitary, hyponormal and co-hyponormal operators.
