Using an open type wind generator, two kinds of tests on TLP models were carried out. One was the wind tunnel tests for measuring both wind load and coefficients and effects of interaction of elements on the coefficients. The other was the test for measuring response of a model with legs installed in the seakeeping basin, where wind and waves were applied both individually and simultaneously. On the other hand, the nonlinear analysis in a time domain was carried out. Based on the comparison of the measured responses with the calculated ones using the experimental coefficients, some foundamental considerations are discussed on the following subjects : possibility of evaluation of wind loads by summing up element loads, feasibility of nonlinear time domain analysis, possibility of superposition of wave and wind loading and so on.