Sonnet is a 14-lined poem in the lyric mood whose subject is mainly about love. Heaney experimented the genre of sonnet in his three books: “Glanmore Sonnets” in Field Work “Clearances” in The Haw Lantern and “Glanmore Revisited” in Seeing Things. These three books have two things in common: the poet have changed his style and subject and that they no longer contain the Northern Troubles. Through reading sonnets selected from Field Work, The Haw Lantern and Seeing Things, I came to the following conclusion: the reason the poet adopted the genre of sonnet is that he wanted to write about love, not hatred or violence after he escaped from massacre of Ulster Trouble. And sonnets of three books depict three different kinds of love: love for family, love for landscape and love for writing. The sonnets of Field Work are characterized by the poet's contrary mind: the sense of relief and the sense of sin because he ran out of the massacre, discarding his relatives and his community. Sonnets in The Haw Lantern on the whole, show his filial piety and affection for his dead mom by trying to remember the moment of being together. Seven sonnets in Seeing Things are the recollection of Glanmore where he settled down with his family and wanted to live in peace, escaping from Ulster turmoil. Meanwhile, these sequence of sonnets have some difference: these sonnets have the different tone: humorous or childlike tone in Field Work, elegiac tone in The Haw Lantern and the recollective tone of Seeing Things.