The permeability of cutting fluids influences cutting effect directly. The main influential factors of cutting fluid penetration in minimum quantity lubrication (MQL) such as nozzle position, spray parameters were analyzed theoretically with spray and fluid mechanics. Based on turning 45 steel tests on CNC super precision machine tool, the cutting effect such as cutting force, surface roughness and chip shape were studied. Theory and tests results show that supplying more cutting fluids from main tool flank at proper position (20mm from cutting point) can get better cutting effect: low cutting force, low surface roughness and easy treated chip.