Using time-dependent density functional theory,we study multi-electron effects on high harmonic generation(HHG) and strong field ionization(SFI) from molecules [1].Both HHG and SFI although related to extreme distortion of an electron wave function in a system in the presence of a strong laser field,were so far successfully studied with theories based on "single active electron"(SAE) approximation such as "Strong Field Approximation".