I'm now having a project which IBM x3550 server (part no.: 797821A), and SAS harddisk x 2 will be used. I'm wondering if Slackware Linux can be installed and run in this server or not. Also, is there any requirement or anything need to be take care? Please kindly help~

You need to find out what the processor/s is/are. What OS does it run now?

x3550 DC Xeon 5110 Processor 1.6GHz/ 1066MHz x 2
- Powerful Intel Xeon 5050 and 5080 dual-core processors
- 1 GB(2 x 512MB FBD)of high speed PC2-5300 ECC double data rate(DDR2)Chipkill™
FBDIMM memory; eight DIMM slots support up to 32 GB
- Choice of open bay HDD configurations:
- Two 3.5 two 3.5-in hot-swap SATA
- Two PCI-Express x8 slots (full height, half length); one slot is convertible to
PCI-X via riser card option 64-bit/133 MHz (full height, half length)
Optional support for PCI-X adapters
- 670-watt, auto-ranging power supply
- Integrated systems management processor
- Integrated dual Gigabit Ethernet
- One serial port (16550A-compatible), four USB ports,
and two video ports (front and rear)
-Light-Path Diagnostics providing an LED map to a failing component
-Predictive Failure Analysis (PFA) supports HDDs, CPUs, VRMs, fans and memory
-IBM Integrated system management processor (ISMP)
IBM 73.4 GB 3.5" 10K SAS Hot-Swap HDD x 2


Please help~

It looks like the processor is likely 64-bit. You could run a 32-bit OS like Slackware with it, but you may also want to consider something like the 64-bit version of Slackware -- Slamd64.