Water pollution caused by the overuse of antibiotics poses a major threat to the natural environment and human health. As a green and environmentally friendly advanced oxidation technology, low-temperature plasma is considered to be one of the most promising antibiotic degradation methods, but it needs to be further improved in terms of degradation efficiency and energy efficiency. In this study, transient spark discharge was obtained by using nanosecond pulse power supply with a needle-water electrode configuration, and applied to tetracycline degradation in water. The effect of pulse voltage, frequency, initial concentration, initial pH value on tetracycline degradation was studied, and the results show that the degradation rate of tetracycline was the highest under the condition that the initial concentration was 50 mg/L, the pulse voltage was 9 kV, the frequency was 2 kHz, the initial pH is neutral, and the degradation rate reached 91.6% when the processing time was 10 min. The energy efficiency and electrical energy per order are 0.165 g·kW^-1·h^-1 and 0.78 kW·h·m^-3, respectively. Free radical quenching experiments showed that hydroxyl radicals (·OH) played a major role in the degradation of tetracycline, while H₂O₂ and O₃ played a slightly weaker role. Cytotoxicity experiments also showed that the toxicity of the solution decreased significantly after 10 min of gas-liquid discharge treatment.