Abstract: Monochamus alternatus is an important pest in wooden packing. In order to use Steinernema feltiae for control of M. alternatus in quarantine treatment, experiments were done to determine the LD₅₀ and LT₅₀ of M. alternatus by S. feltiae. Analysis showed that, for older larva, TDM (Time-dose-mortality model) was P_i1=1-exp[2.9957+0.0747lg(d_i)], LD₅₀ was 1.2767 nematodes per M. alternatus, and LT₅₀ was 1.6716 d; for pupa, TDM was P_i1=1-exp[-3.7567+0.2377lg(d_i)], LD₅₀ was 1.4417 nematodes per M. alternatus, LT₅₀ was 1.2627 d. Results showed that LD₅₀ decreased when the test time extended, and LT₅₀ shortened when dosage of S. feltiae increased. Host searching efficiency analysis revealed that M. alternatus could easily find S. feltiae when they were 4-10 cm away. Control efficacy of S. feltiae against M. alternatus by different application methods of S. feltiae ranked as soaking, sponge and injection.