As banned veterinary drugs, many pesticides, including malachite green (MG), pose a risk of carcinogenesis. Due to its low price and strong antiseptic qualities, MG has been used illegally in fisheries. As a result, MG residues are usually detected in fresh fish. To evaluate MG residues, currently, approaches include high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and other methods are used, and the detections are performed using a small volume of aquaculture water. However, such traditional detections rely on large and expensive equipment, which are cumbersome, and their processes are complicated, time-consuming and expensive. Consequently, these traditional methods cannot meet the needs of on-site detection of pesticides in markets, which are with features of large circulation, fast speed and low price. In recent years, with the emergence of surface-enhanced Raman scattering (SERS) and portable Raman spectrometers, a rapid on-site detection method for trace pesticide molecules becomes possible. Herein, the SERS technology uses surface plasmon of metallic nanostructures to sense molecules located nearby, thus obtaining information of molecular species and concentrations. In order to achieve an extremely low limit of detection(LOD), generally, the coffee ring effect or other means are used on SERS substrates to enrich molecules into a certain region sufficiently. When a droplet contact the substrate for a hydrophilic substrate, the liquid spreads on the surface, leading to a long perimeter of its coffee ring and a decrease in molecular distribution concentration. While when a superhydrophobic substrate is used for molecule enrichment, due to its small surface adhesion, droplets are unable to be fixed and would roll on the surface, thus shall significantly increase the difficulty of operation. Taking detection of trace residues of MG molecule as an example, due to the noisy environment caused by people in the market, collisions occur from time to time, and due to the lack of professional experiment platforms in the market, it is not desirable to use a superhydrophobic SERS substrate to detect pesticide molecules under this condition. A SERS substrate based on parahydrophobic nanostructures is proposed for rapid on-site trace detection of MG molecules in this work. Compared with previous superhydrophobic substrates, parahydrophobic substrates presented herein is able to firmly grasp droplets to be measured, which perfectly solves the problem that in on-site detections, droplets roll on conventional supehydrophobic substrates. In addition, compared with the hydrophilic substrates, due to a large contact angle of the parahydrophobic substrate, the area of the coffee ring can be reduced by 5.73 times, thus enriching concentration of the molecules can be largely increased, which as a result, can ultimately reduce LOD by at least two orders of magnitude. In short, the parahydrophobic SERS substrate proposed in this work is expected to be applied in rapid on-site detections of trace pesticide molecules.