This study explores the function of the affixes -en and -ing that could influence the theta-roles of verbs to which the affixes are attached. The two affixes often appear in the synthetic compounds in English. The results are as follows. First, the affixes -en and -ing link the theta-role realized in the subject of the verb to the noun followed, which is proposed as Theta-linking Principle: that is, the affixes -en and -ing link the theta-role realized in the subject of the verb to the noun followed. Second, in the synthetic compounds including the affixes -en and -ing, the left element must not be the subject of the verb, which is the Synthetic Compound Constraint. And the affix -er link thematic roles of the sentential subject, such as Agent, Instrument. Thus, this study aims to find out the function of the affixes on the point of lexical functional approach.