when this NIC works at 1Gbps ,everythins is perfect，and very stable.
but,when it works at 100mpbs ,full duplex mode, packets lost about 15%-25%
set it to 100mpbs half duplex mode then everything works fine.

I tried 2 DGE-530T cards,and one tplink made by the same marvell 8001 chip
they act the same way

When you configure side A for a link to 100mbit / full-duplex you lose the negotiation function. Therefore side B of the link doesn't know the duplex capabilities of side A. As a result side B will configure itself to half-duplex.
Now side A doesn't use the CSMA/CD mechanism to avoid collisions (CSMA/CD is not needed on full-duplex links) while side B does.
When side A wants to send a packet it doesn't check if the line is 'free'. When side B sends a packet at the same time as A they will collide and that packet gets corrupted => packetloss.

What I want to say is: If you manually configure duplex settings on an interface, ALWAYS configure the same duplex setting on the other side.

I 'm sure nothing wrong with my config .
Wan side connect a media converters(Fiber to 100mbps Ethernet UTP)
Lan side connect to a Netgear GS724T switche
and I have to setup a switche port to "sniffer port" for a network monitor device to log internet trafic
the bad thing is ...this "network monitor device" only have a 10/100m NIC ,and that NIC can NOT be replaced.

I used Routeros 3.21 with 2 intel 100Mbps NIC,both of them running at 100mbps fulld uplex ,and everything work fine
but routeros 5.0beta1 can't work with those 2 intel NIC ,I have to replace them ...there for I bought DGE-530T.