Hydromulching is a new mulch product which has positive effects on soil moisture conservation and the inhibition of evaporation. However, current research on its soil moisture conservation effect has mainly adopted the field fixed-point observation method, rather than revealing the soil moisture conservation mechanism from the microstructure of the hydromulching. This paper applied spectrum analysis technology to observe the structure and micromorphological features of hydromulching, which will be able to reveal the mechanism of soil moisture conservation. Three types of hydromulching, based on laboratory preparation, were used to analyze the mechanism of soil moisture, using the infrared spectrometer (FTIR) and environmental scanning electron microscope (ESEM). The results showed that −OH generates intermolecular hydrogen bonds between carboxymethylcellulose sodium (CMC) and polyvinyl alcohol (PVA); the hydrogen bonds were formatted between the molecules of the two components, strengthening their compatibility, which increased the effectiveness of the hydromulching and created a dense mesh structure. ESEM observation results showed that preparation 1's hydromulching coverage had good effects, while preparations 2 and 3 performed poorly. Therefore, we can conclude that hydromulching effectively cements soil particles. Then it can generate the soil membrane structure to reduce evaporation and improve soil moisture conservation function.