  We study the singular set of a codimension one holomorphic foliations on
$\mathbb{P}^3$. We find a local normal form of a codimension two component of
the singular set that is not of Kupka type. We also determined the number of
non-Kupka points immersed in a codimension two component of the singular set of
a codimension one foliation on $\mathbb{P}^3$.

Algebraic Geometry;Complex Variables;Dynamical Systems