Abstract: Abstract: In lakes, reservoirs, rivers, estuaries, aquaculture ponds and sewage treatment plants where the dissolved oxygen concentration needs to be increased, aerator is the most important oxygen equipment to maintain the dynamic balance of dissolved oxygen. Among different kinds of aeration facilities, the microporous aeration aerator has been more widely used, because of its large ventilation capacity, strong oxygenation capacity, energy saving and environmental protection, easy installation and strong adaptability. There are many factors that affect the aeration performance of microporous aeration aerator, mainly including external factors and self factors. The microporous aeration aerator uses a microporous aeration tube as its diffuser, but the current study of the effect of the type of the diffuser on the aeration performance of the microporous aeration aerator is almost blank. And conventionally, the microporous diffuser always uses disc-type, but this way is empirically and even blindly adopted. Therefore, in order to explore the effect of the microporous diffuser with different shapes on the oxygenation performance, a series of oxygenation experiments were carried out under different types of air diffuser rolled up by a same length (1.1 m) of aeration tube in laboratory. The type of the microporous diffuser was the main influence factor. The types were linear-type, C-type, S-type and disc-type. The experimental apparatus mainly included glass tank, microporous aeration system, dissolved oxygen meter and computer. The size of the glass tank was 2 m × 0.8 m × 0.8 m (length × width × height). The test was based on the standard test method for oxygen from American Society of Civil Engineers (ASCE) in different water depth and air flow. The air flow rate was set as 0.6, 0.9, 1.2, 1.5, and 1.8 m3/h and the water depth was set as 0.4, 0.55, and 0.7 m. The results show that, under the same water depth and air flow rate, the oxygen volumetric mass transfer coefficient, standard oxygen transfer rate, standard aeration efficiency and standard oxygen transfer efficiency of the linear-type microporous aeration diffuser are the highest. In the 0.7 m water depth, the ranges of the 4 technical indices are 0.853-1.762 h?1, 8.701-17.432 g/h, 4.146-6.869 kg/(kW·h), and 3.257%-4.912%, respectively, while the S-type is the lowest, and the range values are 0.798-1.504 h?1, 6.850-12.627 g/h, 2.630-4.444 kg/(kW·h), and 2.339%-3.823%, respectively. Between the linear-type and S-type microporous aeration diffuser are the C-type and disc-type. The same law is also obtained at another depth of water. It meant that the oxygenation performance of linear-type was the best, while the lowest one was the S-type microporous aeration diffuser. It could be known that it is not the best for the oxygenation effect of the disc-type microporous diffuser, which we have chosen empirically. After the film was covered on the top of tank to cut off the air-free water surface oxygen mass transfer, the values of oxygen volumetric mass transfer coefficients of these 4 types of diffusers were decreased and the degree of descent was different, and the largest decline rates were 12.29%, 8.73%, 12.26% and 6.74%, respectively. So, the influence degree of air-free water surface oxygen transfer on different diffuser types is different. But the best oxygenation effect occurred still under linear-type microporous aeration diffuser, followed by the C-type and disc-type, and the S-type is still the lowest one. And the values of oxygen volumetric mass transfer coefficients in 0.7 m water depth of linear-type microporous aeration diffuser, C-type and disc-type and S-type are 1.693, 1.470, 1.438 and 1.227 h?1, respectively. Therefore, oxygen performance of linear-type microporous aeration diffuser is the best. Based on these conclusions, for the shallow water to oxygenate, the linear-type microporous aeration diffuser is the first to use as aeration equipment, which provides a certain reference value for us in the practical selection of microporous diffuser shape.