combinatorial testing is an effective black box testing technique for the system with large numbers of parameters and their values. However, for significantly complex and key systems, combinatorial testing still owns high complexity. Testing completely the core part of these systems usually is a kind of solution and Variable strength combinatorial test data generation (VS-CTDG) emerges. In this paper, enhanced bird swarm algorithm (EBSA), a variant of Bird Swarm Algorithm (BSA), is employed into the problem. Moreover, a testing requirement reduction is proposed and makes EBSA more suitable into VS-CTDG than ever. Through benchmarks, EBSA is proved an effective approach.