A frameless stereotactic robot-assisted system allows stereoelectroencephalography (SEEG) electrodes to span multiple lobes. As the angularity and length are increased, maintaining accuracy of the electrodes becomes more challenging. The goal of this study was to analyze the factors that influence the accuracy of multilobe-spanning SEEG electrodes inserted using a frameless stereotactic robot-assisted system. A total of 322 SEEG electrodes were implanted in 39 patients with refractory epilepsy, and sixtyone multilobe-spanning SEEG electrodes were selected to analyze the factors that influenced the accuracy of implantation. The target error, entrance error, depth error, and angular error were calculated by a specialized computer program. Factors including electrode depth, angular deviation, referencing method, head holder choice, and use of a predrill procedure were analyzed to determine their effects on accuracy. Thirty-nine patients (aged 2-35 years, median: 19 years; 21 females) underwent frameless robotassisted SEEG electrode implantation. The mean distance between the intended target and actual tip location was 2.57±1.70 mm (range, 0.42-9.02 mm). The mean distance between the intended entrance point and the actual location was 2.2±1.29 mm (range, 0.70-6.13 mm). The mean length of the electrodes was 84.63±7.61 mm (range, 70.60-103.99 mm). The depth error was 1.36±1.22 mm (range, 0.03-6.69 mm), and the angular deviation was 1.64±1.12 degrees (range, 0.15-4.93 degrees). Multifactor regression analysis showed that entrance error, electrode depth, depth error, angular deviation, referencing method, and head holder choice could explain 59.5% of the electrode target error. Angular deviation, choice of registration approach and head holder and the use of a predrill procedure could explain 48.1% of the electrode entrance error. Use of a predrill procedure significantly reduced the electrode angular deviation (P<0.05). Head holder choice, use of a predrill procedure and angular deviation are the primary influencing factors of the accuracy of multilobe-spanning SEEG electrode placement. The Leksell frame and a predrill procedure can be used to increase the accuracy of SEEG electrode placement.