A novel dimethylethanolamine amination polychloromethyl styrene nano-latex coated capillary column were successfully prepared.It was applied to establish OT-CEC methods for determination of four antibiotics: tetracycline (TC),oxytetracycline (OTC),doxycycline (DC) and chlorotetracycline (CTC) in pig plasma.The resolution of four antibiotics with coated capillary column was better than unmodified capillary column at the same condition (Figure 1).We compared four kinds of buffer solution such as Na2HPO4+ citric acid,glycine +HCl,potassium acid phthalate + HCl and HAc+NaAc.When HAc+NaAc was choosen as buffer solution,the electrophoretic current and joule heating were lower than the others.And the resolution of four antibiotics was also better.The optimized electrophoresis conditions were buffer: 295 mmol/L HAc+ 3.3 mmol/L NaAc,pH=2.83,capillary 50 μm i.d.× 50 cm (effective length 41.5 cm),field amplified sample injection: 10 kV× 20 s,water-plug: 30 mbar × 10 s,separation voltage: 18 kV,column temperature: 25℃,UV detection wavelength: 270 nm.The antibiotics were extracted with the solution of 295 mmol/L HAc + 3 g/L NaAc + 4 g/L EDTA-2Na (pH=2.81).The FASS-OT-CEC method was validated in terms of linearity,sensitivity,selectivity,precision and accuracy.The LODs ranged from 3 to 7 μg/L,The recoveries for TC,OTC,DC and CTC were all more than 80% with repeatabilities below 6.2%.Both TC (19.03μg/L) and DC (92.52μg/L) were detected out in the pig plasma samples (Figure 2).