This paper is concerned with the time decay estimates of the fourth order Schrodinger operator $H=\Delta^{2}+V(x)$ in dimension three, where $V(x)$ is a real valued decaying potential. Assume that zero is a regular point or the first kind resonance of $H$, and $H$ has no positive eigenvalues, we established the following time optimal decay estimates of $e^{-itH}$ with a regular term $H^{\alpha/4}$:
$$\|H^{\alpha/4}e^{-itH}P_{ac}(H)\|_{L^1-L^\infty}\lesssim |t|^{-\frac{3+\alpha}{4}}, \quad 0 \leq \alpha \leq 3.$$
When zero is the second or third kind resonance of $H$, their decay will be significantly changed. We remark that such improved time decay estimates with the extra regular term $H^{\alpha/4}$ will be interesting in the well-posedness and scattering of nonlinear fourth order Schrodinger equations with potentials.