The palm solid waste consisting of midribs, stems, shells, mesocarp fibers, and empty bunches has been processed and developed, but not optimal enough. In Indonesia, present study, examined bio-oil product from oil palm shells because its lignocellulose materials that contains roughly 30% of cellulose. The conversion of biomass into bio-oil carried out by a fast pyrolysis process which is a thermal decomposition of biomass in an oxygen-free condition with a short holding time (1-6 seconds) in atmospheric pressure where the volatile components from raw materials quenched from 400-550°C to 15°C and produced residual char and ash. Commonly, the fast pyrolysis could be carried out in a fluidized bed mode operation and required high rate and energy of inert N2 carrier gas. This study provides a solution to combine the fast pyrolysis process with looping technique, utilizing the recycle of inert carrier gas during the operation to maintain energy savings. The product distribution of compounds produced from pyrolysis of biomass is highly depending on various factors namely the kind of biomass, mode of pyrolysis process, pyrolysis conditions and the holding time of pyrolytic products leaving the pyrolysis reactor. The usage of fast pyrolysis operation mode is mainly intended to recover the pyrolytic product in the initial stage of the decomposition of biomass. This purpose is realized by employing the method of conditioning the shorter holding time, so that the pyrolytic product as soon as possible leaving the high temperature pyrolysis reactor. This case must be hindered due to the high temperature condition caused the occurring of secondary reaction of pyrolytic products in the reactor and the further reaction decomposition in gas phase reaction leads to undesired products. The purpose of this research work is to observe the change of product distribution in bio-oil consisting of a mixture of aldehydes, ketones, acids, furans, phenols, and anhydrous sugars such as levoglucosan. The composition contained in bio-oil resulting from combined fast pyrolysis process has read in Gas Chromatograph-Mass Spectrometry (GC-MS) diagram. The product distribution of compounds in the bio-oil varies according to a specific operating conditions (holding time, temperature) and focused on further optimization process in the fast pyrolysis operation. With the variation of pre-treatment of the biomass at 100°C, this study shows that furan group produced through the secondary cracking of cellulose. Another variation of the pyrolysis holding time shows that the phenol and acetic acid (up to 40% area) are the most obtained products with compositions depended on each pyrolysis holding time.