This paper deals with the effect of doping concentration in p+ deep well on charge sharing in 90nm dual well CMOS technology. TCAD simulation results show doping concentration in p+ deep well has a more significant effect on charge sharing in PMOS tube than in NMOS tube. By increasing doping concentration of p+ deep well appropriately, the charge sharing in PMOS can be restrained effectively, which is useful for reinforcing the charge sharing.