Caenorhabditis elegans is one kind of the most important modal animals for studying heredity, development and behaviors, and for investigating the mechanisms underlying from molecular to systematic levels. Gene microinjection and integration are the most important ways to make transgenic animals in C. elegans. They are widely used in the studies of expression, function and interaction of genes. Briefly, a DNA construct (plasmid or cosmid) or PCR product which carried gene(s) of interest is mixed with a co-injection marker and injected into the distal gonad (syncytium) through a micropipette. The DNA injected is taken up into the mature oocytes and exists as an unintegrated extrachromosomal array, which segregates randomly and can be lost. The extrachromosomal arrays are integrated optionally into chromosomes by irradiation of γ rays, X rays, or by TMP/UV integration method. Here, the detail processes and key points of microinjection and gene integration in C. elegans was introduced and the know-how in these techniques was offered.