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s The two dimensional CP 1 model with θ term is simulated. We compute the topological charge distribution P (Q) by employing the “set method” and “trial function method”, which are effective in the calculations for very wide range of Q and large volume. The distribution P (Q) shows the Gaussian behavior in the small β (inverse coupling constant) region and deviates from it in the large β region. The free energy and its moment are calculated as a function of θ. For small β, the partition function is given by the elliptic * e-mail:[email protected] ** e-mail:[email protected] *** e-mail:[email protected] theta function, and the distribution of its zeros on the complex θ plane leads to the first order phase transition at θ = π. In the large β region, on the other hand, this first order phase transition disappears, but definite conclusion concerning the transition is not reached due to large errors.