Four kinds of weft knitted fabrics made of silver-plating yarn were taken as samples and their conductivities were tested under weft tensile to investigate the relationships between tensile property and resistance. The results are the following: the resistance of fabric has a linear relationship with strain within a definite range; as for strain sensitivity, vertical stripe interlock with silver-plating and wool yarn, horizontal stripe interlock fabric with silver-plating and wool yarn fabric is the most remarkable one, plain fabrics with silverplating and spandex comes second, and plain fabric with silver-plating yarn is the least;the change of contact resistance among yarns during stretching caused different fabric sensitive to strain; when the interlock fabrics were stretched repeatedly to simulate the heartbeat signals, their resistances remained stable at a value, so they can satisfy the stability requirement.