The electrical performance of a package is extremely important for high speed digital system operations. CSP(chip scale package) is known to have better electrical performance than the convnetional packages. In this paper, the electrical performance of the BLP(bottom leaded plastic) package, a kind of CSP, has been alayzed by both simulation and real measurement. The electrical perfdormance of a BLP was compared with that of the conventioanl TSOP(thin small outline package). The leadinductanceand lead capacitance were used for the comparison purposes. The new BLP design provides much better electrical performance that TSOP package. It has about 40% favorable parameter values.