Phyllotaxis and morphological characteristics of monocotyledonous and tricotyledonous mutants （found during cultivation process） and dicotyledonous plants of Helianthus annuus Linn. were observed. The results show that numbers of monocotyledonous， dicotyledonous and tricotyledonous plants are 8， 339 and 3， respectively in 350 cultivated plants of H. annuus， accounting for 2.3％， 96.9％ and 0.9％ of total individual number， respectively， and their corresponding phyllotaxis is alternate， opposite and whorled types， respectively. Monocotyledonous plant has the fewest leaf number， the most leaf layer number， and the largest flower diameter； tricotyledonous plant has the most leaf number， the fewest leaf layer number， and the smallest flower diameter. There is no obvious difference in plant height of individuals with different cotyledon types. It is suggested that cotyledon number of H. annuus is obviously correlated with phyllotaxis type.