Combined with opaque predicate,control flow obfuscation enables semantics-preserving transformations,which can achieve the purpose of code protection.However,existing opaque predicate is easily attacked by symbolic execution and has the problem of small symbolic variable.To solve the above problems,combined with symbolic variable and array,this paper designs the conditional expression of inequality by single array nesting and modulo add operation of symbolic variable,based on which an algorithm for constructing opaque predicate without size constraints is proposed.The opaque predicate obfuscation based on the proposed algorithm can incur not only false negative but also false positive issues to attackers,which effectively defends against symbolic execution attacks.Besides,the potency,resilience and cost of the program obfuscated by opaque predicate without size constraints are experimentally tested and analyzed by measuring procedures such as opaque predicate detection,bogus control flow removal and so on.Experimental results show that the opaque predicate obfuscation based on the proposed algorithm not only demonstrates excellent potency and efficient cost,but also has high resilience to anti-deobfuscation in new test environment.