According to the problem that it was difficult to analyze the leakage of straight through labyrinth seals of hydraulic cylinder, k-ε turbulent model was used to calculate the leakage of the labyrinth seal in piston rod guide sleeve based on PHOENICS software. The influences of groove number, groove depth, groove width and groove distance on leakage were analyzed, which correctness was verified by using the groove friction coefficient curve. It is shown that groove width is about 20~30 times of clearance, groove depth is about 3~5 times of clearance, groove distance is greater than 50 times of clearance, the groove depth to width ratio is about 0.2 and the groove distance to width ratio is greater than 2.5 have better effect on preventing leakage.