This study evaluates the effect of percutaneous electrical nerve stimulation (PENS) and transcutaneous nerve stimulation (TENS) for pain relieving in patients with liver cancer. Patients will randomly allocated into PENS group, Tens group and control group.

PENS and TENS have been reported with analgesic effect in patients with pain, including cancer pain, lower back pain, neck pain, stomachache and so on. Effect and mechanism of PENS on pain relieving has been widely researched. With additional electrical stimulation in certain frequency and intensity to conventional acupuncture, pain controlling effect has been largely enhanced. However, invasive operation limits its application and acceptability, especially on pancreatic cancer. TENS is an advanced technique generated from PENS, which is much more welcome for its noninvasive character. Further more, its analgesic effect on cancer pain has been proved by several multi-central, randomized, clinical trials.

Inclusion Criteria:

• Primary liver cancer with pain;
• Haven't underwent neurolytic celiac plexus block in the past 1 month;
• With anticipatory survival of more than 3 months.

Exclusion Criteria:

• Metastatic liver cancer;
• Can not tolerate a flat or side lying or sitting prostrate for 30 min;
• performance score>3;
• Who has been recruited in other clinical trial for pain relieving;
• Who underwent radiotherapy or local radioactive seeds implantation for pain relieving in the past month;
• Imaging diagnosed with encephalic tumor or metastasis;
• Who with cardiac pacemaker or metal stand;

Participant is allocated randomly by staff A, and grouping situation is concealed; Technician (stuff B) or chargeing docotor operates PENS or TENS, or administers oral analgesic medication; Related datas are collected according to perdetermined forms by stuff C; Outcomes are assessed by stuff D.