Abstract: Carbon nanotubes (CNTs) were pretreated by purification, sensitization and activation in turn, and then electroless copper plated in plating solution at different pH values (7-13) with NaBH₄ as reductant. Micromorphology and chemical composition of the CNTs treated at different stages were studied, and influence of plating solution pH value on copper plating effect was analyzed. The results show that after purification treatment, the impurity particles on the surface of CNTs disappeared, and the phase was pure CNTs. After sensitization treatement, a sensitized layer composed of continuous particles was formed on the surface of CNTs. These particles were mainly Sn(OH)₂, Sn(OH)Cl and SnO particles. After activation treatment, the activation layer consisted of continuous and relatively fine particles, and these particles were mainly palladium and SnO particles. With increasing pH value of the plating solution, the reducing ability of NaBH₄ increased, so the amount of copper particles on the surface of CNTs increased. When the pH value reached 11, a continuous uniform copper plating was formed. But when the pH value increased to 13, discontinuous copper particles with relatively large size were formed on the surface of CNTs.