Experimental study on heat transfer performance of circumferential overlap trisection helical baffle heat exchangers of tilt angles 12°, 16°, 20°, 24°and 28° compared with a segmental baffle heat exchanger are conducted. The testing heat exchangers are constructed of a common cylinder case and replaceable tube bundle cores. The hot fluid is heat transfer oil with about 70 ℃ in the shell side and the cold fluid is cooling water with about 11 ℃ in the tube side. The results show that within the testing range, the overall heat transfer coefficient, the shell side heat transfer coefficient, pressure drop as well as comprehensive indexes ho/Δpo and ho/Δpo1/3 decrease with the increase of the tilt angle of the baffles, and the optimum scheme is the one with baffle tilt angle of 12°, and the ratios of the mean values of the shell side heat transfer coefficient ho, comprehensive index ho/Δpo and ho/Δpo1/3 of the helical scheme with baffle tilt angle of 12° over those of the segmental baffle scheme are 1.253, 1.391 and 1.285, respectively.