In this paper we have presented the simulation and analysis of the channel field, potential, mobility, hole concentration, and the threshold voltage of pentacene thin film transistor with gate metal work function and gate insulator thickness. The top contact transistor from pentacene active material, paryelene dielectric and gold source/drain electrodes, has been used for our simulation. The simulations have been performed using Silvaco’s Atlas device simulator. The Poole-Frenkel transport model was used in the pentacene active material. The results of the simulation have shown an impact of the gate metal work function on threshold voltage, channel potential, channel charge concentration, channel field, and mobility of the device.