Taiwan is a nation of small-scale economy agricultural sector has been protected by government for a long time by high tariff, tariff quotas and subsidy policy domestically. The agricultural sector is the most important sector of many economics and highly protective acts were practiced in this sector. Therefore the World Trade Organization (WTO) in particular allows imported countries to proceed with temporary protective activities-"Special Safeguard clause". However, Taiwan needs to follow the results of WTO negotiation after participating WTO. For executing the promise of WTO negotiation results, we have to decrease import tariff among relevant products and cancel policies of trade protection such as import control and domestic subsidy. Particularly in agricultural products, it is the major goal to reduce tariff between WTO members. We will face the challenge of low-price products from outside countries, making policy fast for dealing with relevant problems and computing out industrial loss in a short time are both worthy for government to pay more attention on it. We try to applied COMPAS model for analysis. In our research, we choose the shiitake as our research targets. We found that producers will have the negative impacts after reducing tariff. Shiitake have more serious effects of price than of amount. This could be resulted from quantity control policy by government, consumer behavior in domestic and quality reorganization from domestic products to foreign products. Government should assist farmers to build up knowledge of branding and processing before foreign low-price products begin to shock domestic market. Excluding strict definition of Safeguard clause, based on different tariff set up, the protection effect of "Safeguard Clause" could be great than of "Special Safeguard Clause" to impose positive effect on domestic firms.