We study the site percolation under Achlioptas process (AP) with a product rule in a 2-dimensional (2D) square lattice. From the measurement of the cluster size distribution, P_s, we find that P_s has a very robust power-law regime followed by a stable hump near the transition threshold. Based on the careful analysis on the P_s distribution, we show that the transition should be discontinuous. The existence of the hysteresis loop in order parameter also verifies that the transition is

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... ous in 2D. Moreover we also show that the transition nature from the product rule is not the same as that from a sum rule in 2D.