On Moment Condition and Center Condition for Abel Equation

In this paper we consider Abel equation $x^{\mathrm{\prime }}=g(t)x^2+f(t)x^3$, where $f$ and $g$ are analytical functions. We proved that if the equation has a center at $x=0$, then the Moment Conditions, i. e., $m_k={\int }_{-1}^{1}f(t)(G(t){)}^{k}dt=0,k=0,1,2$, is satisfied where $G(t)={\int }_{-1}^{t}g(s)ds$. Besides, we give partial a positive answer to a conjecture proposed by Y. Lijun and T. Yun in 2001.