Palladium nanoparticles (PdNPs) modified boron-doped diamond (BDD) electrode was simply fabricated via electrodeposition technique for the sensitive electro-analysis of four beta-agonist compounds, including terbutaline (TER), salbutamol (SAL), ractopamine (RAC), and clenbuterol (CLB) after a prior separation by ultra-high performance liquid chromatography (UHPLC). The separation was carried out using a reverse phase C18 column with gradient elution of appropriate proportion between methanol and phosphate buffer solution (PBS) pH 7.0 at a flow rate of 1.0 min mL(-1). The following electrochemical detection (ECD) was accomplished by amperometric method with a detection potential of 1.0 V vs Ag/AgCl. The modified BDD electrode, unlike other carbon-based electrodes used for beta-agonists detection, typically showed the superior anti-fouling ability and provided excellent long-term stability, resulting in no complicated cleaning steps needed during each determination. The measurement of beta-agonists using the PdNPs modified BDD electrode integrated with UHPLC showed a linear relationship in the range of 0.2 to 200 mu g mL(-1) with detection limits of 0.04, 0.02, and 0.03 mu g mL(-1) for TER, SAL, and RAC, respectively. Meanwhile, CLB displayed linearly in the range of 0.5 to 200 mu g mL(-1) with a detection limit of 0.19 mu g mL(-1). Moreover, this method was successfully applied to detect beta-agonists in diverse samples, including swine feed, swine meat, and human urine with satisfied recoveries in the range from 80.5% to 110.0%. Reliability of this developed method was also validated with ultra-high performance liquid chromatography coupled with ultra-violet detection (UHPLC-UV), and the results showed highly quantitative agreement between the two methods. Therefore, the PdNPs modified BDD could be productively utilized as effective electrodes, with good electrocatalytic activity of PdNPs towards beta-agonists oxidation and favorable anti-fouling performance of BDD. The simultaneous detection of four beta-agonists by UHPLC-ECD exhibited good stability, acceptable reusability, high sensitivity and rapid analysis.