Tidal current energy shows great attractiveness as it stores an enormous amount of predictable sustainable resources that can be extracted and used for commercial power generation. The present study aims at investigating the performance of a 300 W counter-rotating type horizontal axis tidal turbine (HATT) by computational fluid dynamic (CFD) and experiments. And this study provides a novel method to test the performance of a tidal current turbine. In the present work, a bi-directional counter-rotating type HATT, the power and blade diameter are 300 W and 1 m respectively, was designed according to blade element momentum theory (BEMT). The CFD simulations, flume experiment tests, and sea trial were carried out to evaluate its performance. The experiment tests include 1/4 prototype blades towing tank model test and prototype large radius rotating arm tank test. The power coefficients of the blades under different blade tip speed ratios were obtained. Results shown that a good agreement has been obtained between the CFD predictions and the experiment data, moreover, the counter-rotating type HATT has a great power output performance. Such results provide valuable data for validating the hydrodynamic design and numerical simulations of counter-rotating type HATT. What's more, this work provides a novel method to test the performance of a tidal current turbine, which is a large-radius rotating arm tank test.