We studied the influence of nanocrystalline silicon (nc-Si) thin film thickness on top gate nc-Si thin film transistor (TFT) fabricated at $180^{circ}C$. The nc-Si thickness affects the characteristics of nc-Si TFT due to the nc-Si growth similar to a columnar. As the thickness of nc-Si increases from 40 nm to 200 nm, the grain size was increased from 20 nm to 40 nm. Having a large grain size, the thick nc-Si TFT surpasses the thin nc-Si TFT in terms of electrical characteristics such as field effect mobility. The channel resistance was decreased due to growth of the grain. We obtained the experimental results that the field effect mobility of the fabricated devices of which nc-Si thickness is 60, 90 and 130 nm are 26, 77 and $119;cm^2/Vsec$, respectively. The leakage current, however, is increased from $7.2{ imes}10^{-10}$ to $1.9{ imes}10^{-8};A$ at $V_{GS}=-4.4;V$ when the nc-Si thickness increases. It is originated from the decrease of the channel resistance.