We study the collapse transition of the lattice homopolymer on a square lattice by calculating the
exact partition function zeros. The exact partition function is obtained by enumerating the number
of possible conformations for each energy value, and the exact distributions of the partition function
zeros are found in the complex temperature plane by solving a polynomial equation.We observe that
the locus of zeros closes in on the positive real axis as the chain length increases, providing the
evidence for the onset of the collapse transition. By analyzing the scaling behavior of the first zero
with the polymer length, we estimate the transition temperature and the crossover exponent.