A multi-walled carbon nanotube (MArNT)/silica xerogel composite was prepared by sol-gel technique and characterized by Raman spectroscopy and transmission electron microscopy. The nonlinear optical property of MWNTs in liquid suspension and solid state matrix were investigated separately by open aperture Z-scan method, using 532 and 1064 nm nanosecond laser pulses. The results show that both MWNT composite and suspension are nonlinear efficient at 1064 and 532 nm, while MWNT composite may be more suitable for practical use because of their better nonlinear effect and possibly nondestructive nonlinear absorption mechanism. (c) 2005 Elsevier B.V. All rights reserved.