Using a graphite rod with a hole filled with the powder of a mixture of Y-Ni alloy and graphite as anode; single-wall carbon nanotubes (SWCNTs) with 50%-70% purity were produced in quantity of tens of grams a day under the are conditions of 40-60 A d.c. and helium pressure of 2 arm. If calcium-nickel was used as catalyst instead of yttrium-nickel, high yields of SWCNTs can also be produced in large quantities, although the yield was slightly less than that of yttrium-nickel. The samples were characterized by SEM, HREM, and Raman spectroscopy. The results showed that the SWCNTs produced with yttrium-nickel as catalyst had the same structures as those obtained from laser-ablation with Co-Ni as catalyst. SWCNTs with smaller diameters were found when calcium-nickel was used as catalyst, proving that the diameter of SWCNTs is dependent on the properties of the metal catalysts. Furthermore, high helium pressure can lead to a high yield of SWCNTs. Our results suggested a formation mechanism of SWCNTs and the roles played by nickel and yttrium or calcium element.