Test application time of IP is based on the maximum scan in/out chains.A well balance wrapper scan chains design is an important approach to minimize the test application time and test cost.Best Fit Decrease (BFD) is the most classical scan chains balance method

which is easy to realize

but the result is not the best.This paper describes a wrapper scan chains balance algorithm base on twice-assigned method by the chains difference.The main idea of the proposed solution is that select a standard chain

with its length

L

find the

chains which length longer than

L

from all internal scan chains of the IP core

compute these chains the difference

di

with L

regard these chains as

L

in the first-assigned.Sort the length shorter than

L

and

di

in descending order of length

assign to the enable shortest wrapper scan chain in the second-assigned.The proposed method is also easy to use

experimental results for the ITC'02 SOC Test Benchmarks show that the method in this paper can get better balanced result when compared to the existing solutions.