To reduce the wear of lip seal of wide-speed hydraulic motor pump and prolong the service life, the lip compression is reduced and the non-contacting labyrinth seal is used as the front stage, forming a series combined dynamic seal (CDS). The reliability of CDS in the wide-speed range is verified by model experiment. Firstly, the structure form and dimension of labyrinth seal with relatively small leakage and heat production were determined by model experiment. Then, by establishing the model of lip seal and simulating the static structure, the relationship between the compression and maximum contact pressure of the lip was obtained. Finally, using the CDS which is formed by combining the different lip seals with the selected labyrinth seal to carry out experiments, the leakage, temperature distribution and lip wear were obtained. The results show that trapezoidal tooth labyrinth seal (TTLS) has better sealing effect and less heat production. When the sealing clearance is 0.1mm and 0.3mm, it accounts for 0.11% and 0.32% of the rotor diameter, respectively. Under the same conditions, the smaller the proportion, the better the sealing effect, but the higher the heat production. With the increase of compression, the maximum sealing pressure first increases and then decreases. When the compression of the lip exceeds 0.1mm, the CDS will not leak significantly in a wide-speed range, but the greater the compression, the faster the temperature rise in the closed cavity. Lip wear is positively correlated with pv and the wear decreases with the decrease of compression.