In construction development, implementation often occurs that is not in accordance with planning due to certain situations and conditions. This affects productivity, implementation methods and implementation time, causing delays in construction operations. Productivity in the construction industry plays an important role in construction activities which has a direct impact on the cost of project completion. Implementation of the lean construction concept, namely the use of prefabricated materials, will greatly increase the productivity of construction project work compared to the use of cast in situ materials such as concrete. This research aims to compare the productivity of concrete slab work for station connecting bridge projects using prefabricated HCS and cast in situ concrete. Data collection on work duration is carried out for each work activity (through observation) which includes HCS installation work and concrete casting work. This research uses Monte Carlo simulation to create artificial duration data and WebCyclone program to help simulate construction work operations. The research results show, with the Precast HCS method, work can be completed within 25.1–30 Calendar Days (1 Month). Meanwhile, with the Cast in Situ method, work lasts 70.3–75 Calendar Days (2.5 Months). In units, the Precast HCS method produces equal to 5.13 min/m3, while the Cast in Situ method requires 15.6 min/m3. Further discussion through the results of previous research also states that the use of modular concepts such as prefabricated materials has advantages in terms of time and quality compared to cast in situ work.