In this talk, we discuss the problem of optimal control design for suppression of singularity via flow advection in chemotaxis modeled by the Patlak- Keller-Segel (PKS) equations. It is well-known that for the system without advection, singularity of the solution may develop at finite time. Specifically, if the initial condition is above certain critical threshold, the solution may blow up at finite time by concentrating positive mass at a single point. In this talk, we will first address the global regularity and stability of the PKS system in the presence of flow advection in a bounded domain, by using a semigroup approach. Then we focus on the design of an optimal flow field for suppressing such singularities. Rigorous theoretical framework and numerical experiments will be presented to demonstrate the ideas.