Unsteady film cooling characteristic from pressure side coolant in squealer tip in turbine stage was investigated by numerical simulation. Due to unsteady flow in turbine stage, flow characteristics and blowing ratio of coolant from various holes fluctuate and change cooling effectiveness on squealer rim, cavity floor and side wall. In unsteady simulation, deterioration of coolant coverage causes unsatisfied cooling performance on squealer tip, which results in the maximum reduction of 18.3% and 20% of cooling effectiveness on squealer rim and cavity floor at specific instants compared to steady simulation. In different moments, pressure side coolant increases average heat transfer coefficient on pressure side squealer rim by 15% ∼ 47% and forms discrete distribution of high heat transfer coefficient there. Unsteady heat transfer on squealer rim is much intense compared to steady condition. Raising blowing ratio and decreasing cavity depth promote cooling effectiveness in tip cavity. Too small blowing ratio might lead to the risk of high temperature mainstream invasion into some pressure side film holes. Cooling effectiveness in tip cavity increases with cavity depth decreasing. Due to relative motion between blade tip and shroud, scraping vortex pushed rolling vortex more closely to pressure side and thus facilitates coolant to touch cavity floor.