||In a North-South trade model with innovation and imitation, we investigate the effects of IPR protection and trade protection. Typically, we show that unlike Southern tariff, Northern tariff supplements IPR protection and is not a beggar-thy-neighbor policy. The optimal Northern tariff rate is higher than in conventional models without innovation. The global welfare rises as Northern tariff increases, but declines as Southern tariff increases. This calls for urgent trade liberalization in the South.