Abstract: There are different power consumption leakage characters for different instructions executed in IC chips. These side channel characters can be used to construct templates for different instructions and different paths a program took at a certain time. And then the side channel signals obtained from an unknown chip would be matched with these side channel templates, and the according to the maximum likelihood theory the best matched candidate may be the most likely correct in struction or path. The simple side channel template analysis against the binary modular exponentiation implementation of RSA executed in a microcontroller (AT89C52) validated the effective of the side channel template analysis in programs′path detection, and the static side channel template analys is against several typical instructions showed that the side channel template analysis is useful and powerful in reverse engineering for cipher chips.